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What affects .22LR match ammo bullet trajectroy?
- Thread starter grauhanen
- Start date
What can cause such bullet behaviour? While MV explains some of it, it doesn't explain it all.
The bottom line is that .22LR bullets often may not fly as expected.
An amateur ballistician, Larry Landerscaper, who has his built own shooting tunnel and a sophisticated chronograph system, has been analyzing .22LR behaviour for well over a decade. His work is applauded and welcomed by the BR shooting community. His posts are not considered controversial and don't generate disagreement from experienced shooters.
In another forum he posted the following comparison of ammo POI at 25 yards and 50 yards.
The location of each shot is colour-coded Red-White-Blue-Dark Green-Light Green for 1-2-3-4-5 respectively at both distances. Group sizes are included for each five shot group at each distance.
Based on their POI at 25 many of the bullets don't strike predictably at 50. This shows that something other than MV variation helps explain .22LR bullet trajectory.
To be sure, Landerscaper and others have noted elsewhere that bullet MV does not alone explain bullet behaviour. What, then, can add to understanding why .22LR bullets often behave unpredictably?
See the posts by HuskerP7M8 (Landerscaper) here: https://www.rimfireaccuracy.com/Forum/index.php?threads/ammo-testing-at-25-yards.28412/page-2
The bottom line is that .22LR bullets often may not fly as expected.
An amateur ballistician, Larry Landerscaper, who has his built own shooting tunnel and a sophisticated chronograph system, has been analyzing .22LR behaviour for well over a decade. His work is applauded and welcomed by the BR shooting community. His posts are not considered controversial and don't generate disagreement from experienced shooters.
In another forum he posted the following comparison of ammo POI at 25 yards and 50 yards.
The location of each shot is colour-coded Red-White-Blue-Dark Green-Light Green for 1-2-3-4-5 respectively at both distances. Group sizes are included for each five shot group at each distance.
Based on their POI at 25 many of the bullets don't strike predictably at 50. This shows that something other than MV variation helps explain .22LR bullet trajectory.
To be sure, Landerscaper and others have noted elsewhere that bullet MV does not alone explain bullet behaviour. What, then, can add to understanding why .22LR bullets often behave unpredictably?
See the posts by HuskerP7M8 (Landerscaper) here: https://www.rimfireaccuracy.com/Forum/index.php?threads/ammo-testing-at-25-yards.28412/page-2
swaged lead bullets can have air trapped inside, causes bullets to wobble in flight and lose stability as they slow down, also create sporadic flight at higher speed and higher rpm, out of balance bullets fly like out of balanced rims roll.......and you can't see the deficiency on either one, but spin it fast enough and it's obvious
yodave is on to something with regard to out-of-balance bullets.
Before diving deeper into bullet "imbalance," however, it may be useful to consider other problems, which may be related to balance but are also problems in and of themselves. Some rounds have hidden flaws, such as imperfectly formed bullet heels, which contribribute to irregular trajectory. Furthermore, bullet crimping and seating may not always be concentric. These can affect ammo performance.
A little over a year ago, a German poster with the moniker "the Stowaway" posted some very informative information about the above on accurateshooter.com. (See https://forum.accurateshooter.com/threads/22-lr-bullet-sorting.4012117/page-3)
Flawed heel characteristics are not good for consistency. In Michael Shea's Rimfire Revolution, Steve Boelter former president of Anschutz North America and author of Rifleman's Guide to Rimfire Ammunition, called the .22LR bullet heel "one of the most critical areas of accuracy in a .22 bullet". The trouble is they are undetectable without using or destroying the round.
The Stowaway also observed that non-concentric bullet crimping was a problem.
According to George Frost in his indispensable book Ammunition Making, proper crimping is "crucial" and the "most complicated" part of the most critical step of seating the bullet.
An example of a non-concentric crimp, below.
A bad concentric crimp
A better concentric crimp
When a bullet is not concentric or is non-concentrically seated, there is more potential for unpredictable bullet trajectory.
All or some of these problems can contribute to a bullet trajectory that isn't always related to it's muzzle velocity.
But this is not all. Potentially related to some of the above factors, there is yet another factor which can can dramatically affect how .22LR bullets fly. It returns to the question of imbalanced bullets -- and the trouble is it can't be seen or measured. It only shows up on the target.
Before diving deeper into bullet "imbalance," however, it may be useful to consider other problems, which may be related to balance but are also problems in and of themselves. Some rounds have hidden flaws, such as imperfectly formed bullet heels, which contribribute to irregular trajectory. Furthermore, bullet crimping and seating may not always be concentric. These can affect ammo performance.
A little over a year ago, a German poster with the moniker "the Stowaway" posted some very informative information about the above on accurateshooter.com. (See https://forum.accurateshooter.com/threads/22-lr-bullet-sorting.4012117/page-3)
Flawed heel characteristics are not good for consistency. In Michael Shea's Rimfire Revolution, Steve Boelter former president of Anschutz North America and author of Rifleman's Guide to Rimfire Ammunition, called the .22LR bullet heel "one of the most critical areas of accuracy in a .22 bullet". The trouble is they are undetectable without using or destroying the round.
The Stowaway also observed that non-concentric bullet crimping was a problem.
According to George Frost in his indispensable book Ammunition Making, proper crimping is "crucial" and the "most complicated" part of the most critical step of seating the bullet.
An example of a non-concentric crimp, below.
A bad concentric crimp
A better concentric crimp
When a bullet is not concentric or is non-concentrically seated, there is more potential for unpredictable bullet trajectory.
All or some of these problems can contribute to a bullet trajectory that isn't always related to it's muzzle velocity.
But this is not all. Potentially related to some of the above factors, there is yet another factor which can can dramatically affect how .22LR bullets fly. It returns to the question of imbalanced bullets -- and the trouble is it can't be seen or measured. It only shows up on the target.
lol
Looking at the targets posted by grauhanen with velocities, we have to consider the chronograph error may account for some of the differences.
In a perfect world a fast shot should hit high and a slow shot low, but then when we consider barrel harmonics, some guys claim they can achieve positive compensation where they happen upon a condition where slow shots are released in a high barrel oscillation and faster shots are released in a lower oscillation The goal being to try to find accuracy in a way that negates the effect of velocity spreads.
If the harmonic node occurs within the error range of the chronograph, it may not be possible to align vertical dispersion with chronograph values.
As for positive compensation, I believe it can happen on occasion by accident and coincidence, but I have no confidence that anyone could deliberately achieve such a balance and repeat it from one day to the next.
In a perfect world a fast shot should hit high and a slow shot low, but then when we consider barrel harmonics, some guys claim they can achieve positive compensation where they happen upon a condition where slow shots are released in a high barrel oscillation and faster shots are released in a lower oscillation The goal being to try to find accuracy in a way that negates the effect of velocity spreads.
If the harmonic node occurs within the error range of the chronograph, it may not be possible to align vertical dispersion with chronograph values.
As for positive compensation, I believe it can happen on occasion by accident and coincidence, but I have no confidence that anyone could deliberately achieve such a balance and repeat it from one day to the next.
Interesting. Available in Canada?
Although the discussion of why .22LR bullets may not always follow predictable trajectories based on MV is far from complete here, it's time to deal with a few extraneous matters and getting them out of the way so they don't further and needlessly divert from the issue at hand.
It's important to accept the fact that with .22LR MV and trajectory don't always match. In a perfect world, faster rounds would strike higher on the target than slower ones. But it doesn't always happen. There's nothing perfect about .22LR ammo. The point of this thread is to understand why some .22LR rounds don't strike the target where their MV suggests they should.
It is possible that there were chronograph errors -- after all it was not a Doppler or Oehler device. The problem is one of having one's cake and eating it too. If errors explain the mismatch of MV and POI, then it follows that the chronograph recorded reasonably correctly only for those shots where MV and POI would seem to match. In other words, can errors explain the mismatch of MV and POI in addition to matching of MV and POI at the same time?
Further, the "harmonic node" and the "error range of the chronograph" are not related here. One occurs on the barrel, the other is a +/- factor within the chronograph. The chronograph measures the MV of each round as best it can, while the node doesn't change.
There's no need to enter into a discussion of positive compensation. It's not relevant here and is the subject for another thread.
On another note,
It's not sold in Canada but can be ordered from the U.S. The G3 model is the best tool available for measuring .22LR base to ogive length if it's something that's needed. I've tried the G3 gauge and found it didn't make a difference. Of course, my own experience is hardly conclusive.
It's worth noting that it's not something that's in use among the most competitive rimfire BR shooters because they don't believe it makes a difference. In high level competition south of the border, no serious BR shooters use it or any other method of sorting ammo -- except for one.
The only method that's proven effective for improving results is to sort ammo by lot performance. Shooters can't shortcut their way to improved accuracy. They don't use rim thickness gauges, concentricity gauges, scales, or base to ogive measuring tools. Despite the obvious appeal of short cuts to improve rifle/ammo performance, they just don't work.
Of course, this is not the thread to debate the merits of any ammo sorting technique. The focus should remain on understanding why .22LR too often doesn't have predictable trajectories.
It's important to accept the fact that with .22LR MV and trajectory don't always match. In a perfect world, faster rounds would strike higher on the target than slower ones. But it doesn't always happen. There's nothing perfect about .22LR ammo. The point of this thread is to understand why some .22LR rounds don't strike the target where their MV suggests they should.
It is possible that there were chronograph errors -- after all it was not a Doppler or Oehler device. The problem is one of having one's cake and eating it too. If errors explain the mismatch of MV and POI, then it follows that the chronograph recorded reasonably correctly only for those shots where MV and POI would seem to match. In other words, can errors explain the mismatch of MV and POI in addition to matching of MV and POI at the same time?
Further, the "harmonic node" and the "error range of the chronograph" are not related here. One occurs on the barrel, the other is a +/- factor within the chronograph. The chronograph measures the MV of each round as best it can, while the node doesn't change.
There's no need to enter into a discussion of positive compensation. It's not relevant here and is the subject for another thread.
On another note,
It's not sold in Canada but can be ordered from the U.S. The G3 model is the best tool available for measuring .22LR base to ogive length if it's something that's needed. I've tried the G3 gauge and found it didn't make a difference. Of course, my own experience is hardly conclusive.
It's worth noting that it's not something that's in use among the most competitive rimfire BR shooters because they don't believe it makes a difference. In high level competition south of the border, no serious BR shooters use it or any other method of sorting ammo -- except for one.
The only method that's proven effective for improving results is to sort ammo by lot performance. Shooters can't shortcut their way to improved accuracy. They don't use rim thickness gauges, concentricity gauges, scales, or base to ogive measuring tools. Despite the obvious appeal of short cuts to improve rifle/ammo performance, they just don't work.
Of course, this is not the thread to debate the merits of any ammo sorting technique. The focus should remain on understanding why .22LR too often doesn't have predictable trajectories.
had friend wanted buy one, not made anymore
Why so quick to dismiss?
You asked what might affect vertical dispersion, well barrel harmonics do... Shot to shot muzzle velocity variation can affect barrel harmonics and by extension... point of impact.
If the harmonic is working a certain way and a slow round was thrown high, then that's a factor that "might" explain some of your POIs.
You cant just arbitrarily dismiss the point. Wether you want to label it as harmonics or positive compensation, it is a factor. The lower the velocity spreads, the less its a factor.
The results in a group are reflective of every variable, not just the ones you want to think about.
This time of year its cold out and temperature changes will also be a significant factor as the lubricants will change coefficient of friction between a cold barrel and as it warms up. That may also affect harmonics.
As noted, it's not relevant here. If positive compensation was occuring without a tuner and completely by chance, your suggestion is that it works for some rounds from the same lot of match ammo but not others from the same lot. That's not how positive compensation works. Please reread yodave's post #28.
In any case, it's not the purpose here to discuss positive compensation. If you wish to expand your understanding of PC and rimfire (and, there seems to be room for that), please start another thread.
The issue here is why .22LR ammo doesn't always have a trajectory predicted by muzzle velocity.
To refocus your attention, keep in mind the question is one of ammo, not barrel harmonics. Some causes are linked to ammo "flaws" such as those outlined in post #24. Except for flaws in the bullet heel, these are identifiable.
But there's still something else, something unintentionally "built in" to the ammo that causes .22LR bullets to "fly" in unexpected ways. The problem isn't measureable or predictable. It affects performance of ammo regardless if it's only one shot or many. Although there may be a barrel-related component in some cases, this is first and foremost an ammo issue.
In fact, it can explain why some lots of ammo continue to produce good results as distance increases and why others don't even after performing very well at closer ranges.
There has been nothing elevating about this discussion. If you wish to discuss what prefer to discuss, please begin another thread.
Your best contribution to this and many other rimfire threads is marred by a limited knowledge that's been confused for an abundance. It's not possible to take your observations seriously when they continue to be factually inebriated and irrelevant.
I come from the world of cast bullet shooting, and don't have piles of experience with .22LR. In centre fire cast bullet shooting the causes of random dispersion seems to be uneven bump up of the bullet by the powder charge. This was demonstrated by a guy by the name of F.W. Mann who performed a bunch of experiments well over a hundred years ago when all bullets were cast or swaged lead. His book is called "The Bullets Flight from Powder to Target".
His writing style is weird, but he basically identified the problem. In short, the soft lead bullet is distorted by the powder charge and changes it's shape to fill the case interior & throat of the rifle chamber. Often this results in a bullet that is no longer perfectly symmetric and therefore wobbles in flight. Wobbling changes the aerodynamics of the bullet and it doesn't hit where it should.
The way modern cast bullet shooters often get around some of this is to use a technique called breech seating which gives the bullet fewer chances to distort improperly.
I imagine some of these ideas are useful to .22LR shooters, but maybe not.
Chris.
His writing style is weird, but he basically identified the problem. In short, the soft lead bullet is distorted by the powder charge and changes it's shape to fill the case interior & throat of the rifle chamber. Often this results in a bullet that is no longer perfectly symmetric and therefore wobbles in flight. Wobbling changes the aerodynamics of the bullet and it doesn't hit where it should.
The way modern cast bullet shooters often get around some of this is to use a technique called breech seating which gives the bullet fewer chances to distort improperly.
I imagine some of these ideas are useful to .22LR shooters, but maybe not.
Chris.
Chris (gunlaker) wins the day as he's on to something very important with the reference to cast bullets. Three types of ammo -- rimfire lead bullets (including copper plated), airgun pellets, and cast -- experience a problem related to what's alluded to above.
The problem is identified in Mann's book from over a century ago and is discussed in Harold Vaughn's Rifle Accuracy Facts originally published in 1998.*
The major cause of dispersion in rimfire, pellets, and cast projectiles is because of center of gravity (Cg) offset. Soft lead projectiles, unlikee jacketed centerfire bullets, can't be manufactured to have no Cg offset. In addition, these soft lead projectiles may experience further changes to the Cg because of variations in obturation near the chamber and as they travel through the bore.
The result of the Cg offset, which may vary between individual rounds of the make and from imperfect chambers/bores is that some .22LR ammo experiences more dispersion with distance than others. In short, the main cause of non-linear spread (groups get larger MOA-wise with distance), is from Cg offsets that can't be avoided. It is "built in" to varying degrees in the bullet manufacturing process and further affected by the changes the bullet undergoes as it travels from leade to muzzle.
*the following is a summary of Vaughn's explanation of Cg offset.
“An offset Cg (Center of Gravity) is forced to rotate about the geometric axis while in the bore of a barrel and this is an unnatural condition.
A spinning projectile will always spin about its principal axis and the principal axis always passes through the projectile Cg, if it’s free to do so.
Due to the Cg offset, a tangential velocity component is produced while the bullet is in the bore.
Consequently, the bullet will start spinning about its principal axis and its Cg the instant it exits the muzzle.
This tangential velocity component creates a lateral drift velocity when the bullet exits the bore.
The direction of this lateral drift velocity will be perpendicular to the plane containing both the geometric and principal axes at the instant of muzzle exit.
With the Cg offset located below the geometric axis in the chamber, the bullet will be deflected 90 deg's to the left and impact at the outer edge of a circle defined by the calculated radius of dispersion.”
(From post #48 h ttps://www.rimfirecentral.com/forums/showthread.php?t=575868&page=4)
Varying Cg offsets, which may be combined by further changes due to bullet obturation as it goes through the bore explains why .22LR ammo, when otherwise unflawed, causes bullet trajectory to be unpredictable.
Unfortunately, these can't be anticipated or measured. But those lots of ammo that shoot better at longer distances than others have less problematic Cg offsets and/or they are shot through barrels that don't further worsen Cg offset.
Unfortunately there is many things the way I see it.
The individual has no control over the ammo production.
No control over rim thickness.
No control over case length.
No control over crimp.
No control over bullet swagging.
No control of the lead period, consistency.
No control of amount of powder.
This can go on and on. Something that we cannot fix. We are at the mercy of lot numbers when it comes to ammo. Some testing of various lots and buy up what you can that is left of that lot. It may not be a 100% lot but that goes for everyone. All one can do to limit the unexplained is a rifle built by someone that understands/studied the requirements of a rimfire rifle. Use of a tuner. Proper technique at the bench or whatever manner you choose to shoot. It gets pretty complex in one sense.
But boiling down to the ammo and the swagging I would say to me the biggest thing would be is how concentric and balanced is that tiny piece of lead? If it is not balanced how could it fly perfectly? Just a thought.
With centerfire and BR there is a reason top shooters swage their own bullets. Off the shell match bullets are good, but not as good as what someone who learns how to swag their own. A key factor is the lead line and the perfect core seat pressure to get good grip yet limit the bleed past the punch. I am no balistician or scientist but sometimes we try to overthink the issue. Like I have said rimfire is a crap shoot beyond 50 yards and I stick to it.
JMO
The individual has no control over the ammo production.
No control over rim thickness.
No control over case length.
No control over crimp.
No control over bullet swagging.
No control of the lead period, consistency.
No control of amount of powder.
This can go on and on. Something that we cannot fix. We are at the mercy of lot numbers when it comes to ammo. Some testing of various lots and buy up what you can that is left of that lot. It may not be a 100% lot but that goes for everyone. All one can do to limit the unexplained is a rifle built by someone that understands/studied the requirements of a rimfire rifle. Use of a tuner. Proper technique at the bench or whatever manner you choose to shoot. It gets pretty complex in one sense.
But boiling down to the ammo and the swagging I would say to me the biggest thing would be is how concentric and balanced is that tiny piece of lead? If it is not balanced how could it fly perfectly? Just a thought.
With centerfire and BR there is a reason top shooters swage their own bullets. Off the shell match bullets are good, but not as good as what someone who learns how to swag their own. A key factor is the lead line and the perfect core seat pressure to get good grip yet limit the bleed past the punch. I am no balistician or scientist but sometimes we try to overthink the issue. Like I have said rimfire is a crap shoot beyond 50 yards and I stick to it.
JMO
You, that is to say we, can buy Eley Tenex or similar high cost stuff, but as a rule I'm not that highly pressed for top accuracy. The thing is, an informed consumer is a demanding consumer, I mean in better ammo times than now. And as a rule, those better times are any time a Republican gets elected president of the USA so let's go Brandon.
