1shotwonder
Member
- Location
- Northwestern Ontario
What is considered to be maximum ROT in a varmint barrel firing this weight of projectile?
Maximum rate of twist for .224 50-55gr projectiles
- Thread starter 1shotwonder
- Start date
Here is a link to a Berger Chart which shows the minimum twist required for each bullet length. It depends on the weight and length, but mostly on the length. And just for clarity a fast twist is 1 turn in 6", while a slow twist is one turn in 14". Short light bullets can use the 14 twist, while long heavy bullets may need as much as 6".
A light bullet is usually most accurate with the slowest twist possible. It still can be shot at a fast twist. The only slight issue is that some bullets in the past would explode after they leave the barrel if they have too fast a twist. I suspect most bullet manufacturers have that solved now. But if you do shoot a light bullet in a fast twist and make no hole in the paper, then you might have blown one up!
223 with a 1-7twist. Fire-forming brass and sighting in scope at the same time. Wouldn't have guessed that the Speer 52gr bullets were going fast enough to fly apart. Watch approximately 25 yards out for for the puff of smoke.
Can't figure out how to embed the video.
Can't figure out how to embed the video.
I think bullet quality comes into play. Cheap plated campros at 3100fps+ out of a 1-7" twist are not long for this world. Jacketed stuff can be loaded accurately though. 1-9" seems to like everything from 40gr up to around 70 in my experience.
I have a l-8 twist Browning in .223. It can shoot 40 grain Hornady V-max bullets, although that isn't what I bought it for. It works very well with 55 grain bullets, similarly 70 grain Speers. Haven't tried anything heavier than the Speers.
Jim
Jim
- Location
- Somewhere on the Hudson Bay Coast
I doubt there is a maximum rate of twist, provided the construction of the bullet can withstand the centrifugal force imparted by very high rotational velocities. Bullets that are intended to expand reliably at Hornet velocities don't stand up particularly well to the rotational velocity imparted by a 1:7 twist; I observed 20% or 30% of Hornady SX and Sierra Blitz turn to dust in the air, and fail to reach their target. But normally constructed bullets don't have a problem, and even short ones are accurate if fired from accurate fast twist barrels. Fast twist barrels tend to produce better terminal performance, game bullets with high rotational velocities, penetrate deeper since they recover from impact induced precession (yaw) more quickly, and varmint bullets tend to be more explosive on impact, for obvious reasons.
The problem with 1:12 and 1:14 twist barrels is that some bullets you expected to be fine, have stability and accuracy problems. A 1:14 won't shoot a 53 gr TSX, and a 1:12 won't shoot a 55 gr Barnes MPG, which is admittedly long for a light weight flat base bullet. If the bullet you choose is short enough to stabilize in the slower twist barrels, its all good, provided you stick with it, or similar bullets, but you certainly give up versatility.
The problem with 1:12 and 1:14 twist barrels is that some bullets you expected to be fine, have stability and accuracy problems. A 1:14 won't shoot a 53 gr TSX, and a 1:12 won't shoot a 55 gr Barnes MPG, which is admittedly long for a light weight flat base bullet. If the bullet you choose is short enough to stabilize in the slower twist barrels, its all good, provided you stick with it, or similar bullets, but you certainly give up versatility.
Cam-Pro .224" bullets are jacketed, rather than plated. However, Remington 55 grain Power-Lokt HPs are plated and are an excellent choice if you want to see bullet blowup out of a 1:7 barrel for yourself. The vast majority of light bullets will work fine out of a fast-twist barrel.
1shotwonder
Member
- Location
- Northwestern Ontario
Ok thank you yes that was my concern that the varmint bullets I plan on using rather than the heavier match bullets would hold together out of the faster twists but seems like a well built varmint bullet in those weights would likely be fine in a 1:9 or 1:10 twist
Running light bullets in fast twist at high velocity can easily result in centrifugal force exploding the bullet before it reaches the target. Just under the ragged edge of rotational self destruction lies a sweet spot in terminal performance though, even if not for accuracy.
But... to answer the OPs question, it depends how fast you want to push the bullet. You can run 40 grain bullets in a 1:7 if they are running slow enough MV.
As for accuracy.... Technically the bullet weight is not the reason light bullets are less accurate in a fast twist barrel. It's just that bullet imperfections are exaggerated at high spin rate.... Think of it like a tire that's out of balance... At slow speeds the tire seems fine, but drive faster and you begin to feel the effect of the imbalance. With a bullet, the imbalance relates to poor accuracy.
Just as you would probably not want to put snow tires on a Ferrari, you would not ideally be using light bullets in a fast twist barrel... even if you "can"
Heavy bullets in a fast twist is like race tires on a race car. Light bullets in a slow twist are a short range combination that neuters the long range performance of the rifle, but is the traditional (cheap to manufacture) solution to short range accuracy.
You might want to look up gyroscopic stability calculators on Google. You'll see the stability is relative to spin rate, velocity and bullet length.
Spin the bullet faster than required can degrade accuracy, but not always. In my experience a slightly over spun high BC bullet seems to be more consistent in switchy winds at long range. The counter point is that a slightly under spun high BC bullet tends to be more accurate in light winds.
But... to answer the OPs question, it depends how fast you want to push the bullet. You can run 40 grain bullets in a 1:7 if they are running slow enough MV.
As for accuracy.... Technically the bullet weight is not the reason light bullets are less accurate in a fast twist barrel. It's just that bullet imperfections are exaggerated at high spin rate.... Think of it like a tire that's out of balance... At slow speeds the tire seems fine, but drive faster and you begin to feel the effect of the imbalance. With a bullet, the imbalance relates to poor accuracy.
Just as you would probably not want to put snow tires on a Ferrari, you would not ideally be using light bullets in a fast twist barrel... even if you "can"
Heavy bullets in a fast twist is like race tires on a race car. Light bullets in a slow twist are a short range combination that neuters the long range performance of the rifle, but is the traditional (cheap to manufacture) solution to short range accuracy.
You might want to look up gyroscopic stability calculators on Google. You'll see the stability is relative to spin rate, velocity and bullet length.
Spin the bullet faster than required can degrade accuracy, but not always. In my experience a slightly over spun high BC bullet seems to be more consistent in switchy winds at long range. The counter point is that a slightly under spun high BC bullet tends to be more accurate in light winds.
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- Location
- Somewhere on the Hudson Bay Coast
I'd like to respond to a couple of your points, beginning with the idea that fast twist combined with high velocity easily results in centrifugal force that explodes the bullet before it reaches the target. This is untrue. What determines whether or not a bullet retains integrity during flight has nothing to do with weight or length, and everything to do with it's construction. Consider the comparison of 3 different bullets, a 55 gr Sierra Blitz, a 52 gr Sierra Matchking, and a 45 gr Barnes TSX. If each is loaded to maximum pressure in a .223, and fired from a 1:7 twist barrel, the bullet that fails to reach the 100 yard target a third of the time is the heavier, slower Blitz, not due to it's light weight or short length, but due to its thin jacket, intended to expand at Hornet velocities. Yet, its the shorter and lighter MK and TSX that are impacting the target at greater velocities, and with higher rotational velocities. I know this from doing it, years before 1:7 twist barrels were offered on factory rifles.
The analogy of a spinning tire and a spinning bullet is an interesting one. The funny thing about a speed wobble is that you can outrun it. A vehicle that vibrates badly at 45-60 mph is certainly unnerving, but once speed increases above 70 mph, everything mellows out. Does the analogy hold up? If the base of the bullet is free of defects, and the bullet is known as a quality product, with a reputation for being uniform in both dimension and weight, chances are its not out of balance, but the terminally anal can check uniformity of weight and runout.
Gyroscopic drift with a given load from a given barrel is a constant; like gravity, it can be calculated and allowed for. If you encounter a wind blowing across your line of sight, a RH twist barrel diminishes the effect of a right to left wind, or conversely, the wind velocity diminishes the gyroscopic drift of the bullet. Such a condition can result in tighter groups, but the opposite wind, at the same velocity, can result in wider groups, since the combined effects of drift are now greater. Note how this remains true, regardless of the rate of twist, or the velocity of the wind. Only the degree of drift changes, its not a question of whether it occurs or not, and unless correctly allowed for, bullet drift, regardless of cause, does affect group size.
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Hmmm….
Interesting perspective Boomer… but let’s roll this around a bit…
You broadly claim that it’s categorically untrue that spinning a light bullet too fast can easily result in bullet failure and that in fact it is actually caused by poorly constructed bullets?
Interesting…
So by your logic, a light bullet that shoots fine from a 1:14 twist barrel but explodes before it goes 100 yards from a 1:7 twist barrel is not actually caused by the fast twist and velocity, but is actually the fault of the bullets???….. Hmmm I’m struggling with this one.
The bullet in this example was fine from a 1:14 but fails from a 1:7…. But the 1:7 works great when used with heavy bullets.
Still struggling with your logic.
You don’t “get” my “tire analogy”…. Well first of all it’s an “analogy” and not a “thesis” on ballistic flight.
What I’m attempting to illustrate is that spinning a poor quality bullet no faster than required to attain gyroscopic stability is where that grade of bullet will perform as well as that grade of bullet can… Spinning such a bullet faster than the minimum will only serve to antagonize the accuracy performance.
Conversely a high grade match bullet can be spinning faster than the minimum required to attain gyroscopic stability and still produce reasonably good groups, but there is always a point that is ideal. Over spinning even a good bullet is not the best way to maximize the accuracy potential of that bullet.
The reality of this is not exactly cutting edge news. It’s quite factual that light/short bullets produce best groups when fired from a slow twist barrel and that heavy/long bullets produce poor accuracy from a slow twist and best accuracy from a fast twist barrel.
So.. no… it’s not a tire, but I thought some of the readers (Boomer exempted) might grasp the parallelism here.
Interesting perspective Boomer… but let’s roll this around a bit…
You broadly claim that it’s categorically untrue that spinning a light bullet too fast can easily result in bullet failure and that in fact it is actually caused by poorly constructed bullets?
Interesting…
So by your logic, a light bullet that shoots fine from a 1:14 twist barrel but explodes before it goes 100 yards from a 1:7 twist barrel is not actually caused by the fast twist and velocity, but is actually the fault of the bullets???….. Hmmm I’m struggling with this one.
The bullet in this example was fine from a 1:14 but fails from a 1:7…. But the 1:7 works great when used with heavy bullets.
Still struggling with your logic.
You don’t “get” my “tire analogy”…. Well first of all it’s an “analogy” and not a “thesis” on ballistic flight.
What I’m attempting to illustrate is that spinning a poor quality bullet no faster than required to attain gyroscopic stability is where that grade of bullet will perform as well as that grade of bullet can… Spinning such a bullet faster than the minimum will only serve to antagonize the accuracy performance.
Conversely a high grade match bullet can be spinning faster than the minimum required to attain gyroscopic stability and still produce reasonably good groups, but there is always a point that is ideal. Over spinning even a good bullet is not the best way to maximize the accuracy potential of that bullet.
The reality of this is not exactly cutting edge news. It’s quite factual that light/short bullets produce best groups when fired from a slow twist barrel and that heavy/long bullets produce poor accuracy from a slow twist and best accuracy from a fast twist barrel.
So.. no… it’s not a tire, but I thought some of the readers (Boomer exempted) might grasp the parallelism here.
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- Location
- Somewhere on the Hudson Bay Coast
There is nothing wrong with the construction of a bullet that is designed to perform well at Hornet velocities. The problem comes from attempting to drive that bullet half again faster than Hornet velocity, combined with the centrifugal forces from a fast twist barrel.
My experience in blowing up bullets is the Sierra 80 Match King. Not exactly a light varmint bullet.
My 22-250 Ackley could launch them as fast as 3400fps. But at that velocity some would blow up.
My suggestion to the OP is that if there is no intention of shooting heavy bullets, a 1:9 or 1:12 would be the best bet. Personally I would use 1:9, to keep the door open for some heavier bullets.
My 22-250 Ackley could launch them as fast as 3400fps. But at that velocity some would blow up.
My suggestion to the OP is that if there is no intention of shooting heavy bullets, a 1:9 or 1:12 would be the best bet. Personally I would use 1:9, to keep the door open for some heavier bullets.
1shotwonder
Member
- Location
- Northwestern Ontario
Thank you yes I don't expect to be firing too heavy of a pill so Im leaning toward a little looser rate of twist
- Location
- Somewhere on the Hudson Bay Coast
That's interesting. I fired thousands of 52 gr MKs from my 1:7 Triple Deuce, albeit with 300 fps less velocity, without incident. The only blow-ups I experienced with that rifle were with thin jacketed Hornady SXs and Sierra Blitzs, about 30% overall failing to get to the target. I wonder if the 80 gr MK has the same jacket thickness as the 52 gr?? This might explain the failure that you observed, of the much longer bullet, fired at a significantly higher velocity. Certainly high velocity plays a role in bullet blow-up, since the forces working on the bullet are proportionately higher. I wouldn't expect any lead core, 40 gr bullet, to survive the 5000 fps velocity possible in a .22/06, and would limit shooting that recipe to mono-metal bullets. Nosler Ballistic Tips have developed a reputation for explosive terminal performance, yet the 55 gr BTs I've fired at 4000 fps, from my 1:7 .243, made it to target, where they made a pleasingly small group, although admittedly I haven't fired enough of them to say they won't fail in a 1:7, but the initial firing looked promising.
OP, I concur with Ganderite on the 1:9. My 1:12 .223 failed to stabilize Barns 55 gr MPGs, and not slightly elongated bullet holes, but full profile keyholes!
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For those that want to dig a little deeper into the issue of bullets going poof before they get to the target due to high spin, I have found some information which gives a little history of the issue. In reading it, I gather in mid 2000's Berger Target bullets were getting the reputation of being susceptible to going poof, when similar Sierra bullets did not. This post is mostly speculation on the potential causes, and it promises some further testing to validate the speculation. I will post some information on the testing in a separate post. For those that do not know, Eric Stecker is the current president of Berger Bullets.
"#1 02-13-2007, 12:09 PM#
Eric Stecker#
Registered User Join Date: May 2006
Posts: 266#
Bullet Failure Causes and Solutions Defined#
--------------------------------------------------------------------------------
As many of you know we have been working on the bullet failure (blow up) situation for some time. I have been collecting data from numerous shooters over the last 2 ½ years ranging from general observations to controlled experiments. At Berger, we have been working with folks at MIT and with other top minds in metallurgy and ballistics. What I have below is a report on what we have learned.
To briefly review, bullet failure is when the bullet does not hit the target anywhere near the expected impact location. (This is not about the unexpected 8 or the fifth shot out of a bug hole group). This result can be observed as a shot that is driven way off course but does make it to the ground, a shot that appears as a puff of smoke 30 yards or more from the muzzle, and everything in between. The shooter can experience bullet failure with several shots or with one shot out of a string.#
The wide range of results and conditions has made it very challenging to sort out the true root cause. The information below is meant to bring the true root causes to the surface. I am not suggesting that these causes exist in every situation; however, they cover the vast majority of bullet failures.
The first two root causes are responsible for the most bullet failures:
Excessive RPM resulting from high velocity and a barrel that has a twist rate much faster than is needed for the bullet used. We are working on determining the general RPM limits for various bullets. This will be a long project, and the data we have now is not enough to publish RPM limits.
Solution: Use twist rates that are the same as or close to (faster) published recommendation. When shooting cartridges that produce higher than normal velocity (high capacity wildcats) consider using twist rates slower than those published since the published twist recommendations are based on velocities achieved by standard cartridges. (How much slower is based on the situation however it will usually be only 1” slower)
Friction that produces heat that exceeds the melting point of lead. This result is observed most often by the puff of “smoke” that will be within the first hundred yards from the muzzle. The “smoke” is in fact molten lead. The puff of molten lead does not always occur during this failure. A core that becomes even slightly plastic will not make it to the target properly.
You have heard me talk about a combination of conditions that produces a failure. I have believed this to be true for a long time but frankly, it has only been recently that we have begun to truly understand what is actually happening. Once we started looking at the possibility of the core melting, all the puzzling information from the various reports began to make sense. This is going to be a lengthy post focused on identifying root causes and their solutions so I will not go into all the various conditions and ranges in which these conditions exist that support these findings.#
The report that our bullets would fail while Sierras would not was particularly puzzling. We have known for a while that making the jacket thicker does not make the jacket significantly stronger. As it turns out, we were looking at it from the wrong point of view. We had been looking at a thicker jacket as being a tougher jacket and this just isn’t true, however when you have a thicker jacket you are moving the lead away from the source of the heat (friction between the barrel and the bullet which is mostly in the area of the rifling, not the grooves). Bullets that have thicker jackets are actually thicker in the base and sidewalls near the base, which moves the lead further away from the heat. This increases the amount of friction that the thicker jacketed bullet can realize before the lead core gets hot enough to melt.#
Since thicker jackets are difficult to make concentric, we have two solutions. The first is that we are going to work on making thicker jackets for our long-range bullets. This is going to take time, as we will not produce jackets that are greater than .0003 TIR in wall thickness variation. This is harder to do with thicker jackets. The bullets we make now shoot very well and there are several ways that this failure-creating friction can be avoided as it has been by many shooters. Avoiding this condition is the second solution.
Solution for avoiding failure-creating heat using our current bullets: The goal is not to slow the bullet down but rather reduce the heat created by the friction. There are several ways to do this. (Keep in mind that each condition is not absolute and in fact works with other conditions to create failure. Since failures occur occasionally when all the conditions work together to create excessive heat we know that it will not take much to insure that failures are avoided)#
First, you can consider your barrel length. It has been found that barrels longer than 28” are capable of produce failure-creating heat. Remember that the bullet is hottest at the muzzle. The more metal the bullet has to travel over, the hotter it gets.#
Second, consider using moly, Danzac (tungsten disulfide), or any other dry lubricant as these reduce friction thereby reducing heat. I know moly is a hot button for many shooters however setting all other things aside it works great as a friction (heat) reducer.#
Third, consider running a patch with a light amount of Kroil through your barrel prior to shooting. This will lubricate the barrel long enough until the carbon builds up enough to serve the same purpose. The first few shots will be erratic, but failure-creating heat is avoided. Barrels that are squeaky clean produce significant levels of friction if no friction reducers are present before firing. (I am not suggesting that you do not clean your barrel completely but rather pointing out how to avoid failure-creating heat when you start shooting).#
Fourth, consider the bore diameter of your barrel (land height not groove depth). Some barrel makers can provide you with different bore diameters. Consider diameters on the larger side of the available options.#
Fifth, consider the land configuration in your barrel. Six groove, cut, squared off rifling produces greater friction than a 5C or 5R type barrel. The 5C or 5R type rifling produces more friction than a three-groove barrel. I am not suggesting one is better than another; however, the friction generated by the different rifling designs should not be ignored.#
Sixth, consider the cartridge you are using. Cartridges such as the 6X284 or any overbore wildcat are notorious for high velocity and barrel life consumption (rapid erosion). These are some of the main ingredients in failure-creating heat generation.
Please remember that the combination of components used in your rifle is a compromise. I have learned why Berger Bullets fail when others do not. I have decided to share this with you because I am committed to enhancing the experience for the shooter and in my opinion, more information is better even if on the surface this information makes us look bad.
Many shooters avoid failure-creating heat when they use Berger and find that Bergers work best for them. You can look at the information above as a reason not to shoot Berger or you can look at it as detailed instructions on how to make Bergers work for you without the concern of producing failures. If you value the accuracy that Bergers produce, then the above information details areas where you can make an easy compromise now that you have all the facts. If you value the conditions listed above that produce failure-creating heat more than you value the accuracy of Berger Bullets, then your decision is also made easier with these details.#
The following root causes are responsible for bullet failures but in smaller numbers:
Human error that produces failure-causing condition. Let’s all admit up front that none of us are perfect. A shooter can create failure-causing condition in the barrel by improper break in, cleaning or storage (crown damage). Failure causing conditions can be created with the load as well. Using the wrong powder, not chamfering necks, excessively tight neck tension damaging the base of the bullet, poor handling practices can also lead to failures. Careful and appropriate firearm handling and loading practices usually avoid these failure causing conditions.#
Tight or rough bore that actually tears jacket material away from the bullet. This is an extreme and rare condition that is easily identifiable with a bore scope, by slugging the barrel or by feeling for a spot that is more resistant to cleaning with a tight patch. Barrel makers are quick to resolve this situation.
Poor bullet fabrication such as too low or too high seating pressure. Low seating pressure can create a poor mechanical bond and/or air pockets that further destabilize the bullet. Seating pressure that is too high effects the copper jacket by producing a weakness where the nose can separate from the body. These conditions can be most easily detected by weighing your bullets, as too low or too high seating pressure is mostly the result of an extreme change in the mass of the lead.
Other examples of poor fabrication are any excessive lube on the cores (many bullet makers do not clean their cores before bullets are swaged) or debris between the jacket and the core can produce a weak bond, air pockets and/or significant stability issues through poor balance around the axis. Another poor fabrication condition that is easiest to avoid is lead that contains debris or significant air pockets due to double extrusion. This condition does not exist when a quality source of lead is used. Quality bullet manufacturers of which there are many can avoid all of these fabrication conditions.
There might be some other causes of bullet failures beyond those listed above but they happen is such rare occurrences that they have not been identified and should not weigh heavily on your mind.
It is my sincere hope that you find this information useful toward enhancing your shooting experience.
Regards,
Eric Stecker
Berger Bullets"
"#1 02-13-2007, 12:09 PM#
Eric Stecker#
Registered User Join Date: May 2006
Posts: 266#
Bullet Failure Causes and Solutions Defined#
--------------------------------------------------------------------------------
As many of you know we have been working on the bullet failure (blow up) situation for some time. I have been collecting data from numerous shooters over the last 2 ½ years ranging from general observations to controlled experiments. At Berger, we have been working with folks at MIT and with other top minds in metallurgy and ballistics. What I have below is a report on what we have learned.
To briefly review, bullet failure is when the bullet does not hit the target anywhere near the expected impact location. (This is not about the unexpected 8 or the fifth shot out of a bug hole group). This result can be observed as a shot that is driven way off course but does make it to the ground, a shot that appears as a puff of smoke 30 yards or more from the muzzle, and everything in between. The shooter can experience bullet failure with several shots or with one shot out of a string.#
The wide range of results and conditions has made it very challenging to sort out the true root cause. The information below is meant to bring the true root causes to the surface. I am not suggesting that these causes exist in every situation; however, they cover the vast majority of bullet failures.
The first two root causes are responsible for the most bullet failures:
Excessive RPM resulting from high velocity and a barrel that has a twist rate much faster than is needed for the bullet used. We are working on determining the general RPM limits for various bullets. This will be a long project, and the data we have now is not enough to publish RPM limits.
Solution: Use twist rates that are the same as or close to (faster) published recommendation. When shooting cartridges that produce higher than normal velocity (high capacity wildcats) consider using twist rates slower than those published since the published twist recommendations are based on velocities achieved by standard cartridges. (How much slower is based on the situation however it will usually be only 1” slower)
Friction that produces heat that exceeds the melting point of lead. This result is observed most often by the puff of “smoke” that will be within the first hundred yards from the muzzle. The “smoke” is in fact molten lead. The puff of molten lead does not always occur during this failure. A core that becomes even slightly plastic will not make it to the target properly.
You have heard me talk about a combination of conditions that produces a failure. I have believed this to be true for a long time but frankly, it has only been recently that we have begun to truly understand what is actually happening. Once we started looking at the possibility of the core melting, all the puzzling information from the various reports began to make sense. This is going to be a lengthy post focused on identifying root causes and their solutions so I will not go into all the various conditions and ranges in which these conditions exist that support these findings.#
The report that our bullets would fail while Sierras would not was particularly puzzling. We have known for a while that making the jacket thicker does not make the jacket significantly stronger. As it turns out, we were looking at it from the wrong point of view. We had been looking at a thicker jacket as being a tougher jacket and this just isn’t true, however when you have a thicker jacket you are moving the lead away from the source of the heat (friction between the barrel and the bullet which is mostly in the area of the rifling, not the grooves). Bullets that have thicker jackets are actually thicker in the base and sidewalls near the base, which moves the lead further away from the heat. This increases the amount of friction that the thicker jacketed bullet can realize before the lead core gets hot enough to melt.#
Since thicker jackets are difficult to make concentric, we have two solutions. The first is that we are going to work on making thicker jackets for our long-range bullets. This is going to take time, as we will not produce jackets that are greater than .0003 TIR in wall thickness variation. This is harder to do with thicker jackets. The bullets we make now shoot very well and there are several ways that this failure-creating friction can be avoided as it has been by many shooters. Avoiding this condition is the second solution.
Solution for avoiding failure-creating heat using our current bullets: The goal is not to slow the bullet down but rather reduce the heat created by the friction. There are several ways to do this. (Keep in mind that each condition is not absolute and in fact works with other conditions to create failure. Since failures occur occasionally when all the conditions work together to create excessive heat we know that it will not take much to insure that failures are avoided)#
First, you can consider your barrel length. It has been found that barrels longer than 28” are capable of produce failure-creating heat. Remember that the bullet is hottest at the muzzle. The more metal the bullet has to travel over, the hotter it gets.#
Second, consider using moly, Danzac (tungsten disulfide), or any other dry lubricant as these reduce friction thereby reducing heat. I know moly is a hot button for many shooters however setting all other things aside it works great as a friction (heat) reducer.#
Third, consider running a patch with a light amount of Kroil through your barrel prior to shooting. This will lubricate the barrel long enough until the carbon builds up enough to serve the same purpose. The first few shots will be erratic, but failure-creating heat is avoided. Barrels that are squeaky clean produce significant levels of friction if no friction reducers are present before firing. (I am not suggesting that you do not clean your barrel completely but rather pointing out how to avoid failure-creating heat when you start shooting).#
Fourth, consider the bore diameter of your barrel (land height not groove depth). Some barrel makers can provide you with different bore diameters. Consider diameters on the larger side of the available options.#
Fifth, consider the land configuration in your barrel. Six groove, cut, squared off rifling produces greater friction than a 5C or 5R type barrel. The 5C or 5R type rifling produces more friction than a three-groove barrel. I am not suggesting one is better than another; however, the friction generated by the different rifling designs should not be ignored.#
Sixth, consider the cartridge you are using. Cartridges such as the 6X284 or any overbore wildcat are notorious for high velocity and barrel life consumption (rapid erosion). These are some of the main ingredients in failure-creating heat generation.
Please remember that the combination of components used in your rifle is a compromise. I have learned why Berger Bullets fail when others do not. I have decided to share this with you because I am committed to enhancing the experience for the shooter and in my opinion, more information is better even if on the surface this information makes us look bad.
Many shooters avoid failure-creating heat when they use Berger and find that Bergers work best for them. You can look at the information above as a reason not to shoot Berger or you can look at it as detailed instructions on how to make Bergers work for you without the concern of producing failures. If you value the accuracy that Bergers produce, then the above information details areas where you can make an easy compromise now that you have all the facts. If you value the conditions listed above that produce failure-creating heat more than you value the accuracy of Berger Bullets, then your decision is also made easier with these details.#
The following root causes are responsible for bullet failures but in smaller numbers:
Human error that produces failure-causing condition. Let’s all admit up front that none of us are perfect. A shooter can create failure-causing condition in the barrel by improper break in, cleaning or storage (crown damage). Failure causing conditions can be created with the load as well. Using the wrong powder, not chamfering necks, excessively tight neck tension damaging the base of the bullet, poor handling practices can also lead to failures. Careful and appropriate firearm handling and loading practices usually avoid these failure causing conditions.#
Tight or rough bore that actually tears jacket material away from the bullet. This is an extreme and rare condition that is easily identifiable with a bore scope, by slugging the barrel or by feeling for a spot that is more resistant to cleaning with a tight patch. Barrel makers are quick to resolve this situation.
Poor bullet fabrication such as too low or too high seating pressure. Low seating pressure can create a poor mechanical bond and/or air pockets that further destabilize the bullet. Seating pressure that is too high effects the copper jacket by producing a weakness where the nose can separate from the body. These conditions can be most easily detected by weighing your bullets, as too low or too high seating pressure is mostly the result of an extreme change in the mass of the lead.
Other examples of poor fabrication are any excessive lube on the cores (many bullet makers do not clean their cores before bullets are swaged) or debris between the jacket and the core can produce a weak bond, air pockets and/or significant stability issues through poor balance around the axis. Another poor fabrication condition that is easiest to avoid is lead that contains debris or significant air pockets due to double extrusion. This condition does not exist when a quality source of lead is used. Quality bullet manufacturers of which there are many can avoid all of these fabrication conditions.
There might be some other causes of bullet failures beyond those listed above but they happen is such rare occurrences that they have not been identified and should not weigh heavily on your mind.
It is my sincere hope that you find this information useful toward enhancing your shooting experience.
Regards,
Eric Stecker
Berger Bullets"
Here is some additional information done by Berger to validate their theories on the cause of bullet failures. It is self explanatory. As an aside, one interesting fact from Berger is that it is harder for them to make thicker jackets meet their quality standard of 0.0003" variance. They have often claimed their hunting bullets which have the lighter jackets are just as accurate as their target bullets. This quality issue, may even imply the hunting bullets could be even more accurate than the target bullets!
My conclusion? I don't think high spin is a serious concern for most casual shooters. However if you have a fast twist 30" barrel, and shoot rapid strings of high velocity shots over and over, with the barrel heating up, you may have bullets go poof unless they have a thick enough jacket to insulate the lead from the heat.
"Berger bullet failure test
First I want to thank Mid Tompkins for doing so much to make this test possible. Without him it would not have happened. Also I want to thank Sherri Hurd and Michelle Gallagher for their part in putting 950 shots down range using a 6.5X284 in a little over 6 hours. You both earned those sore shoulders.
On January 3rd at Ben Avery Shooting Facility in Phoenix, AZ we (in my opinion) solved the bullet failure issue. We conducted a test during which 220 Berger 6.5mm 140 gr VLD made with regular J4 jackets were fired in two different barrels. After these rounds were fired we shot another 220 rounds of Berger 6.5mm 140 gr VLD made with thicker J4 jackets. The results were interesting to say the least.#
Two barrels that had been provided by Krieger were chambered by Mid Tompkins. These barrels were put on two F-Class rifles (Mid's and Bob Mead's). A front rest, rear bag and shooting mat were used in shooting these rifles F-Class style.#
Mid and Michelle spent much of the holidays loading the 950 rounds shot during this test. The ammo was loaded in Lapua cases with 49.5 gr of H4350.#
Present during the test were Mid Tompkins, Michelle Gallagher, Sherri Hurd, Jeremy Hurd, Bob Jones, Alan Elliot, Walt Berger and I. We made sure that for each shot there were at least two people watching through spotting scopes. All shots were documented.
The goal was to shoot all the rounds in highly abusive conditions and then observe if the bullets would fail. We did not alter the barrels or the load in an attempt to create failures on purpose. These barrels and loads were in every way in the same condition when we started as any combination would be on match day.
The procedure used for this test was to fire 20 rounds with one rifle then quickly switch to the other rifle. We would shoot all 220 (in each barrel) of the regular jacket bullets first then shoot all 220 of the thicker jackets. This course of fire was meant to duplicate match type strings and the rapid firing was to produce the harshest conditions possible for the bullets.#
As you can imagine the barrels were very hot to the touch once we got through the first few strings of 20 shots. They would remain hot for the rest of the day.
We started with the .257 barrel first. We were not testing barrels so observations made about the barrels are secondary to the focus of the test. I mention this because I predicted that the .257 bore diameter would produce fewer failures since it was larger than the .256 bore diameter. I was proven wrong.
The .257 bore diameter barrel produced the first bullet failure at shot 106. The .256 bore diameter barrel produced its first bullet failure at shot 151. Even more interesting was the fact that the .257 barrel produced a total of 27 failures (with regular jacket bullets) right up to the last shot. The .256 barrel produced only 12 failures and stopped producing failures when the barrel was cleaned after shot 180. 40 shots were fired after both barrels were cleaned.
Now for the good news. After we finished shooting the bullets made with regular jackets we switched to the thicker jackets. Again both barrels shot 220 each by shooting a string of 20 and then switching to the other rifle. ALL 220 BULLETS MADE WITH THICKER J4 JACKETS (IN BOTH BARRELS) MADE IT TO THE IMPACT BERM.
So that we did not destroy one of Mid's target frames the scopes were adjusted so that we could aim on a target but the bullets would hit the impact area of the next target. At the beginning of the thick jacket shooting we did shoot one 10 shot string on the target. The results were a 12 oclock 6 due to scope adjustment, 8-Xs and 1-10 (string shot by Michelle G.) Accuracy was not the focus of this test but it looked good for ten shots (once we got the scope adjusted).
To verify that something had not changed in the barrel for the thicker bullets we shot another 20 bullets made on the regular jackets in the .257 barrel after the thicker jacket shooting was completed. 9 out of 20 shots fired did not make it to the berm.
Another interesting result was that while we were shooting the thicker jacketed bullets both barrels produced several blown primers. The .257 barrel produced 14 blown primers and the .256 barrel produced 5. There were no blown primers while shooting the regular jacket bullets. We did chronograph five shots using regular bullets at a MV range of 2,996 to 3,024 fps. The chronograph was not working later in the day so we could not check the MV produced when shooting the thicker jacket bullets.
We continued shooting after thoroughly cleaning the .257 barrel using moly coated bullets made with regular jackets. 50 rounds were fired with 14 failures. It is my opinion that the abuse this barrel had experienced does not allow for an appropriate testing of the effectiveness of moly. These bullets were shot mostly out of curiosity. It is certainly clear that moly is not a cure all for bullet failure however I still believe that it helps reduce friction which is the cause of these bullet failures.
It is my conclusion that bullets made with thicker jackets are more capable of sustaining significantly higher levels of abuse before producing a failure. We are gong to do this same test again but this time we will use Bartlein barrels. The purpose again is not to test the barrels but to focus on the results produced by using jackets of different thicknesses.
Even though we are going to conduct another test we are already working on the production of a full line of VLD-THICK bullets in 6.5mm, 6mm, 22 cal and 7mm which will be specifically meant for target competition shooters. I will attempt to attach a detailed report of the specifics of the test.
Regards,
Eric"
My conclusion? I don't think high spin is a serious concern for most casual shooters. However if you have a fast twist 30" barrel, and shoot rapid strings of high velocity shots over and over, with the barrel heating up, you may have bullets go poof unless they have a thick enough jacket to insulate the lead from the heat.
"Berger bullet failure test
First I want to thank Mid Tompkins for doing so much to make this test possible. Without him it would not have happened. Also I want to thank Sherri Hurd and Michelle Gallagher for their part in putting 950 shots down range using a 6.5X284 in a little over 6 hours. You both earned those sore shoulders.
On January 3rd at Ben Avery Shooting Facility in Phoenix, AZ we (in my opinion) solved the bullet failure issue. We conducted a test during which 220 Berger 6.5mm 140 gr VLD made with regular J4 jackets were fired in two different barrels. After these rounds were fired we shot another 220 rounds of Berger 6.5mm 140 gr VLD made with thicker J4 jackets. The results were interesting to say the least.#
Two barrels that had been provided by Krieger were chambered by Mid Tompkins. These barrels were put on two F-Class rifles (Mid's and Bob Mead's). A front rest, rear bag and shooting mat were used in shooting these rifles F-Class style.#
Mid and Michelle spent much of the holidays loading the 950 rounds shot during this test. The ammo was loaded in Lapua cases with 49.5 gr of H4350.#
Present during the test were Mid Tompkins, Michelle Gallagher, Sherri Hurd, Jeremy Hurd, Bob Jones, Alan Elliot, Walt Berger and I. We made sure that for each shot there were at least two people watching through spotting scopes. All shots were documented.
The goal was to shoot all the rounds in highly abusive conditions and then observe if the bullets would fail. We did not alter the barrels or the load in an attempt to create failures on purpose. These barrels and loads were in every way in the same condition when we started as any combination would be on match day.
The procedure used for this test was to fire 20 rounds with one rifle then quickly switch to the other rifle. We would shoot all 220 (in each barrel) of the regular jacket bullets first then shoot all 220 of the thicker jackets. This course of fire was meant to duplicate match type strings and the rapid firing was to produce the harshest conditions possible for the bullets.#
As you can imagine the barrels were very hot to the touch once we got through the first few strings of 20 shots. They would remain hot for the rest of the day.
We started with the .257 barrel first. We were not testing barrels so observations made about the barrels are secondary to the focus of the test. I mention this because I predicted that the .257 bore diameter would produce fewer failures since it was larger than the .256 bore diameter. I was proven wrong.
The .257 bore diameter barrel produced the first bullet failure at shot 106. The .256 bore diameter barrel produced its first bullet failure at shot 151. Even more interesting was the fact that the .257 barrel produced a total of 27 failures (with regular jacket bullets) right up to the last shot. The .256 barrel produced only 12 failures and stopped producing failures when the barrel was cleaned after shot 180. 40 shots were fired after both barrels were cleaned.
Now for the good news. After we finished shooting the bullets made with regular jackets we switched to the thicker jackets. Again both barrels shot 220 each by shooting a string of 20 and then switching to the other rifle. ALL 220 BULLETS MADE WITH THICKER J4 JACKETS (IN BOTH BARRELS) MADE IT TO THE IMPACT BERM.
So that we did not destroy one of Mid's target frames the scopes were adjusted so that we could aim on a target but the bullets would hit the impact area of the next target. At the beginning of the thick jacket shooting we did shoot one 10 shot string on the target. The results were a 12 oclock 6 due to scope adjustment, 8-Xs and 1-10 (string shot by Michelle G.) Accuracy was not the focus of this test but it looked good for ten shots (once we got the scope adjusted).
To verify that something had not changed in the barrel for the thicker bullets we shot another 20 bullets made on the regular jackets in the .257 barrel after the thicker jacket shooting was completed. 9 out of 20 shots fired did not make it to the berm.
Another interesting result was that while we were shooting the thicker jacketed bullets both barrels produced several blown primers. The .257 barrel produced 14 blown primers and the .256 barrel produced 5. There were no blown primers while shooting the regular jacket bullets. We did chronograph five shots using regular bullets at a MV range of 2,996 to 3,024 fps. The chronograph was not working later in the day so we could not check the MV produced when shooting the thicker jacket bullets.
We continued shooting after thoroughly cleaning the .257 barrel using moly coated bullets made with regular jackets. 50 rounds were fired with 14 failures. It is my opinion that the abuse this barrel had experienced does not allow for an appropriate testing of the effectiveness of moly. These bullets were shot mostly out of curiosity. It is certainly clear that moly is not a cure all for bullet failure however I still believe that it helps reduce friction which is the cause of these bullet failures.
It is my conclusion that bullets made with thicker jackets are more capable of sustaining significantly higher levels of abuse before producing a failure. We are gong to do this same test again but this time we will use Bartlein barrels. The purpose again is not to test the barrels but to focus on the results produced by using jackets of different thicknesses.
Even though we are going to conduct another test we are already working on the production of a full line of VLD-THICK bullets in 6.5mm, 6mm, 22 cal and 7mm which will be specifically meant for target competition shooters. I will attempt to attach a detailed report of the specifics of the test.
Regards,
Eric"
coleman1495
CGN Ultra frequent flyer
- Location
- Whitecourt
I could see how cheaper bullets would be more likely to come apart. I know that the accuracy versus twist rate is dependant on bullet quality. The 1-8 twist of a Tikka shoots 55gr federal FMJ like crap basically spraying them all over the place.I am guessing over stabilization. A 53gr V-Max however works great and goes like a laser.
If their was more imperfections in the bullets balance you should get more of an effect from higher twist rate.
If their was more imperfections in the bullets balance you should get more of an effect from higher twist rate.
