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High Pressure Loads in 700 LA

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Unread 03-21-2006, 06:48 PM
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Join Date: Jan 2005
Posts: 126
Re: High Pressure Loads in 700 LA

No.I think you are trolling.
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Unread 03-21-2006, 07:12 PM
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Join Date: Dec 2005
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Re: High Pressure Loads in 700 LA

You're not off base and I don't have a fire extinguisher ready. You bring up a good point.

The tensile strength of most modern centerfire bolt actions is in the 120K to 150K range. Remington and Winchesters are in the middle of that range. I remember this from an article many years ago. Bolt lug hardness and steel type is typically enough for about 140K ppsi.

Proof pressure for the .308 Win. is about 90,000 ppsi but it's normal operating max pressure is about 63,000 ppsi. Many modern cartridges have similar numbers. That's a ways from setting the bolt lugs forward or recess faces back even if several proof loads are fired. I've seen some fired proof load cases and they wouldn't hold a primer.

Dan Lilja's web site has some info on bolt strength.
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Unread 03-22-2006, 09:54 AM
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Re: High Pressure Loads in 700 LA


Most cases will have their primer pockets loosen up at around 65,000 psi depending on the chamber fit to some degree. Some will loosen at a bit less, some a bit more. The 338 Lapua case from Lapua is probably the strongest case I have every used and it will even loosen primer pockets at around 70,000 to 75,000 psi no matter how tight the chamber is fitted.

Point being, you are correct, the case and primer are the weak link here. All will fail well before 100,000 psi, which is a good thing.

Another tid bit of information. In gunsmithing school the topic of detonation came up. If you learn about this occurance with large capacity case designs you would NEVER push a load to primer pocket loosening levels ever again.

Basically what happens is that once the internal pressures reach a point of around 70,000 to 75,000 psi, detonation occurs. What detonation is is when all the remaining powder in the chamber and bore burn nearly instantaneously because of this pressure level.

In most cases, there is not a dramatic amount of powder remaining when this occurs so the results are not dramatic, generally a loosened primer pocket.

In extreme cases where there is a very large case capacity and relatively small bore, serious strain can be imposed on a receiver.

Using the correct burn rate of powder will greatly control any serious happenings but if you use a powder that is a bit quicker then it should be for a specific case volume you can get into trouble.

Actually using a burn rate slightly slower then needed will generally always keep you out of trouble. The reason why, because you simply can not reach this 75,000 psi range with the amount of powder you can fit in the case with proper weight bullets used.

Point being, load to pressures that are under what will loosen a primer pocket. If your getting at least 3 firings per case without loosening primer pockets your in good shape, top load levels but good shape.

If you need more performance, get a larger engine to do the work.

I would tend to agree with you 100%.

Kirby Allen(50)
Kirby Allen(50)

Allen Precision Shooting
Home of the Allen Magnum, Allen Xpress and Allen Tactical Wildcats and the Painkiller Muzzle brakes.

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