The World of Cartridges and Compromises........

What powder an what degree (%) of compression?

I have found that ball/spherical powders when compressed will form into a somewhat solid mass, this is noticed when bullets are pulled and an attempt to dump the powder out, essentially it needs to be scraped out with a dental pick.

I routinely compress my 6 Dasher to 112% with a 'stick' powder. Also, the 9.3x66 Sako I have runs 8-10% compressed with VV N-550 which are duplicate factory loads.

If a solid mass of powder is blocking the shoulder/neck area then this means that the full charge is not ignited, only partially.

Has the rifle in question had the bolt lugs lapped?
 
What is the length of the bullet? I estimated it at 1.58".

Predicted velocity, 20" bbl is 2387 ft/s
59,505 psi
112% load density with Retumbo

What mechanical tweaking have you done to the rifle?
 
Boomer said:
Except that the program does not take case volume into account when compressed loads of slow burning propellants like Retumbo and R-25 are used. So not only have I stopped using Quickload, I've also stopped using loads that exceed 100% loading density.
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Yes it does. Case volume measured in grains of water. Now if you load to 112% of case volume the powder will produce a certain and same volume of gas. Pressure will be higher in a smaller container with the same amount of gas.

QL does not do everything for you, like many industrial computor programs you have to take knowledge to the table.
 
Boomer said:
Provided that cheek-weld, firmness of hold, and the loads are uniform from shot to shot, and the sights are correctly zeroed for range, I'm not sure why recoil imposed muzzle lift matters. However, some rifles don't boresight particularly well, which I assumed had to do entirely with barrel harmonics, but perhaps recoil also plays a part in the equation. It has been my opinion that recoil doesn't occur until the bullet exits the barrel, or from the cylinder of a revolver, but it makes sense that some energy is imposed on the rifle as the bullet accelerates through the barrel. But then it also follows that some of that energy should also be expressed as torque from the rotational velocity imposed upon a heavy bullet, similarly as when you accelerate an engine and you observe it twist against it's mounts. Yet even when shooting hard kicking rifles, torque is seldom felt until you get up to those approaching .50 caliber with bullets that weigh more than 500 grs. Smaller cartridges like the .44 magnum impose noticeable torque when fired in lightweight handguns. My .458 (500 @ 2150) doesn't torque to any noticeable degree, but the .470 and .500s I've shot do, perhaps due to the SXS barrel configuration. Provided that recoil generated linear and rotational rifle velocity, occurring before the bullet exits the barrel, is small enough to be mitigated by sight adjustment, a rifleman never really notices them.
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Check out newton's 3rd Law of Motion
 
Boomer said:
I'm not telling anyone else how to load their ammo, but I am telling you that I do have the evidence to show that that Quick Load predictions for compressed loads of slow burning powder are unsafe. There was no going from moderate pressure to a flattened primer or a stiff bolt lift, it went from moderate pressure and 2350 fps to ka-boom and 2550, in a single step, despite having proceeded carefully and incrementally. The 602's receiver deformed, and its locking lugs compressed.

By the way you've misspoken. You won't get into trouble using light loads of fast burning powder, I frequently use a pinch of Unique, 2400, or SR-4759 to make plinking and small game loads in large cartridge rifles, and you can safely reduce loads of 4895 to 60% of maximum . Although difficult to replicate, where problems have arisen is when light loads of slow burning powder are loaded into bottle neck cartridges. Under the force of the primer, the powder column is driven into the shoulder area of the cartridge, compresses, and forms an unmoveable plug. The pressure then builds beyond the limits of the rifle's strength, and it comes apart. That is a very different set of circumstances than I experienced.
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That is a physical impossibility. The primer ignites the powder , the flame front begins to turn the powder into a gas immediately but not all the powder is turned into a gas right away,talking mS here, it doe not take a lot of pressure (gas contained in a space) to get the bullet to move as it does the moving bullet creates a larger space for more gas to be created by the burning powder and at the same time keeping max pressure within design limits.
That's why there are many different burn rates of powder, looking for a controlled sequence of turning a solid into a gas.
 
Boomer said:
Perhaps I got a pound of Retumbo that came from a lot that was on the fast side of the spec. But even if that was the case, it doesn't account for the difference between the 2350 fps load that showed normal pressure, and a Kaboom from a single grain increment, and a velocity increase of 200 fps. As Ackley stated with respect to problems associated with light loads of slow burning powder in large bottleneck cases, the phenomenon is difficult to replicate, even in a controlled environment. In fact for years he didn't believe it, and thought something else was responsible for the Kabooms; eventually he came around.

Clearly something happened here, and while I can only guess as the cause, it had nothing to do with either my components, (other than perhaps my choice of powder) or with my loading technique. The one element that stands out is the weight of my bullet; a .375/380 equates to a .243/160! I wonder how many calibers long that one would be??!!
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Something to consider in the future, develop a mid range (psi) load through QL, fire 5 shots and record velocities, manipulate the the program so QL prediction matches the actual in the field test. Now you have a base line for any changes that you make or any different lots of the same components.
 
Do you charge a case then seat the bullet or do you charge all the cases then seat the bullets? I seat the bullet as I charge each case

This could be your problem right here ^^^ you being doing this a long time, your balance beam scale is probably been used a lot, there is a real possibility the scale hung up on that weigh, but you will never know because you have not given yourself for an opportunity for a visual check as compared to all the other filled cases.

A practiced eye can tell a few grains difference in charge volumes when looking at several at the same time as they sit in the loading block.

This is why I have never charged cases and seated as one operation. Charge all the cases, visually inspect, check again as each bullet is seated.

thank me later :)
 
hoytcanon said:
What an onerous read... what was this thread about again?
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It started with mental masturbation while sanding the wife's closet, sort of morphed into why did my gun go kaboomfka, lots of theories why it wasn't my fault, some solutions offered, stated distrust of computers....................a good rifle/cartridge combo for mountain elephant hunting, very generous target so no mention of the need of a 6x24 scope with an 88mm OL.
 
BCBRAD said:
It started with mental masturbation while sanding the wife's closet, sort of morphed into why did my gun go kaboomfka, lots of theories why it wasn't my fault, some solutions offered, stated distrust of computers....................a good rifle/cartridge combo for mountain elephant hunting, very generous target so no mention of the need of a 6x24 scope with an 88mm OL.
Click to expand...

A 6X24 has a 24mm OL... a 6-24 may have an 88mm OL...

See how it feels...

Sure, I knew what you meant...
 
BCBRAD said:
What is the length of the bullet? I estimated it at 1.58".

Predicted velocity, 20" bbl is 2387 ft/s
59,505 psi
112% load density with Retumbo

What mechanical tweaking have you done to the rifle?
Click to expand...

The bullet length is 1.595"

The barrel was a Smith fluted stainless 1:10 barrel, with a quarter rib, and the muzzle turned down to flush mount a barrel band front sight. Nothing was done to the action.

Give that load a try and let me know how it works out for you.
 
BCBRAD said:
Yes it does. Case volume measured in grains of water. Now if you load to 112% of case volume the powder will produce a certain and same volume of gas. Pressure will be higher in a smaller container with the same amount of gas.

QL does not do everything for you, like many industrial computor programs you have to take knowledge to the table.
Click to expand...

Your faith in Quick Load is touching. Try that load, blow up your rifle, and see if your point of view isn't modified.
 
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BCBRAD said:
That is a physical impossibility. The primer ignites the powder , the flame front begins to turn the powder into a gas immediately but not all the powder is turned into a gas right away,talking mS here, it doe not take a lot of pressure (gas contained in a space) to get the bullet to move as it does the moving bullet creates a larger space for more gas to be created by the burning powder and at the same time keeping max pressure within design limits.
That's why there are many different burn rates of powder, looking for a controlled sequence of turning a solid into a gas.
Click to expand...

You are mistaken. If the powder in the neck shoulder area has been compressed into a solid mass, which affects its burning rate. I'm suggesting that a solid mass of powder is slower to ignite, and the pressure under it increases until its critical density is exceeded, and is thus rendered inert. A layer of inert material that formed in the shoulder is a plug.
 
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BCBRAD said:
Do you charge a case then seat the bullet or do you charge all the cases then seat the bullets? I seat the bullet as I charge each case

This could be your problem right here ^^^ you being doing this a long time, your balance beam scale is probably been used a lot, there is a real possibility the scale hung up on that weigh, but you will never know because you have not given yourself for an opportunity for a visual check as compared to all the other filled cases.

A practiced eye can tell a few grains difference in charge volumes when looking at several at the same time as they sit in the loading block.

This is why I have never charged cases and seated as one operation. Charge all the cases, visually inspect, check again as each bullet is seated.

thank me later :)
Click to expand...

So you are suggesting that a balance beam scale that is zeroed to the exact charge weight, that must produce 2 consecutive, identical reading has hung up. I don't think so. I disagree with your loading technique. There is no need to visually inspect a load that fills the case, although it is beneficial when loading reduced rifle loads with pistol powder. Having a cartridge block on the bench that is full of charged cartridges is just asking for contamination if you get called away before finishing, to say nothing of what is going to happen to you if the light bulb above your bench explodes. For a smart guy, you take some unnecessary chances, but it doesn't matter, your loading career is over once you shoot that safe load you just got from QL.
 
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It might be interesting to make up a couple of loads identical to the kaboom load, let them sit the same amount of time that the original one did before firing, then pull the bullets with a collet puller and inspect the powder.
 
Boomer said:
If the powder in the neck shoulder area has been compressed into a solid mass, which affects its burning rate. I'm suggesting that a solid mass of powder is slower to ignite, and the pressure under it increases until its critical density is exceeded, and is thus rendered inert. A layer of inert material that formed in the shoulder is a plug.
Click to expand...

Boomer, do you think this situation could happen in other cartridges, such as a 270, 7mm or 300mag. Or is it unique to a 375 ultra sized cartridge and its large diameter bullet creating more potential force on the charge weight .
 
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