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The first sign of excessive pressure is...

 
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  #43  
Old 07-02-2013, 10:27 PM
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Re: The first sign of excessive pressure is...

PBR driver, what if a new case is .0005" larger in diameter than a previously fired factory round before its fired in your chamber? It'll be larger than that after a reduced load's fired in it.

There's a few thousandths inch tolerance in both new case and chamber diameters. And all brass does not have the same metalurgy makeup. Different makes will expand differnt amounts with the same peak pressure in a given chamber and barrel.
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  #44  
Old 07-04-2013, 12:18 AM
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Re: The first sign of excessive pressure is...

Quote:
Originally Posted by AJ Peacock View Post
He discusses both measuring difficulties as well as brass hardening in the article. I was very impressed with the article and it changed the way I did things. I'll be interested to find out what your impression of the information is.

Take care,
AJ
Ok, so, if you would, please explain the velocity idea. I'm not sure I understand. Are you looking for a jump from what listed velocities are, or are you looking for a sudden increase as you work a load up? I've never heard of looking at velocities for pressure signs.
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  #45  
Old 07-04-2013, 07:49 AM
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Re: The first sign of excessive pressure is...

I believe someone could get a box of SAAMI "standard reference" ammo from a supplier listed in:

http://www.saami.org/specifications_...wnload/206.pdf

starting on page 221.

Use this in your barrel with a chronograph and see what the velocity is at the 15-foot standard distance. If you barrel shoots it faster than its specs, your barrel's inside dimensions are such that peak pressure's probably higher than SAAMI spec's; lower if less than.

The following's the latest SAAMI specs for centerfire rifle cartridges' pressure and velocity numbers in SAAMI spec test barrel's bore, groove and chamber specs:

http://www.saami.org/specifications_...essure_CfR.pdf
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  #46  
Old 07-08-2013, 09:32 AM
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Re: The first sign of excessive pressure is...

I'm wondering why the SAAMI chart starts way up in the 6mm range and doesn't include the 243Win.

Also, no mention is made of barrel length which of course affects velocity.

What does it mean when there are 3 velocities listed for 1 bullet weight, like the 130gr under 270Win?

How much variance is allowed in barrel diameters?
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