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pressure sign discusssion

 
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Old 06-30-2004, 09:14 PM
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Join Date: Nov 2003
Location: Washington State
Posts: 2,459
pressure sign discusssion

Hi all,

What do folks use to determine the upper limit of pressure you are willing to load to? Hmm...the reloading books, of course...some say to load no higher than what the book says no matter what. Just as many say the max in reloading books are well below max for liability, etc., reasons. One conversation I had recently with a Hodgdon rep said that their max loads are at 97% of SAAMI average max pressure and that the handloader might get a bit more out of a given load than the book shows, fyi.

I watch my primer for cratering and flattening and the case head for ejector pin marks. A question is, given the batch of brass (hard or soft, etc.) and the rifle/caliber you have, how much can you depend on ejector pin marks as signs of high pressure? Some folks I've talked to say that unless you see the lettering on the case head start to get moved/smudge/whatever or get an obvious shiny mark, you're OK. Others say you shouldn't see the slightest of case head marks...ever...even if there isn't a shiny portion to the mark. Where is the pressure "line" that you shouldn't cross? For me, I've been using the "shiny mark" as the highest and I'll find a load somewhere below considering the amount of primer cratering and flattening as well. What do other folks do?

I've also heard guys say that in the bigger cases, say a 300 RUM, a slight ejector pin mark where the brass isn't flowing (i.e. apparently not moving/smudging/disfiguring lettering on the casehead or leaving an obvious shiny mark)is OK as those big calibers "do that". However, he said that in a smaller cartridge like with a .308 Winchester, you shouldn't see any ejector pin marks. ???? So can various degrees of ejector pin marks mean different things in different calibers in general? Hmmm...not sure about that.

Then you can start talking about primer pockets loosening up. And that every gun is different...

Then there are the guys who are all set up to measure actual pressure when firing the rifle--this would seem to be the safest. But most of us don't have this equipment so what do do in it's stead?

Let's hear from the guys that have been reloading and experimenting with wildcats longer than I've been alive that don't use pressure testing equipment or that can compare what pressure testing equipment says to the observations of primers and case heads after firing. What signs do they look for that indicate pressure is too high and what are the driving principles behind their decisions concerning the look of the primer and the look of the case head?

I'm just curious to see what other folks do and what drives their decisions.

Thanks,

Jon Denham
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Old 07-01-2004, 01:36 AM
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Join Date: Jan 2004
Location: New Castle colorado
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Re: pressure sign discusssion

Like you, I primarily watch my primers and ejector pin marks. I have found that usually, but not always, before primers become smeared against the bolt face I start getting ejector pin marks. When I get pin marks I back off until they are no longer present in warm temperatures. I have used this rule of thumb in several cartridges from .22-250 to .300 Jarrett over the past 29 years. I get long case life and primer pockets stay tight. I usually find best accuracy comes somewhere below max loads anyway. The one exception I am currently shooting is the .300 Jarrett. Max loads of RL22 are very accurate, but when the temps get into the 70's, I'll get an occasional deep pin mark, so I usually load 77 gr unless I'm fooling around blasting prairie dogs with it in the summer sun, then I drop to 75 gr, but the rifle does shoot best at max. I have had a few experiences over the years experimenting with loads that were showing what I considered early preasure signs, when suddenly I would get a sticky bolt or a severly mashed and cratered primer, usually coupled with pin marks that were deep enough to shear a little brass when the bolt was opened. [img]images/icons/shocked.gif[/img] Things can happen fast at the upper end of the preasure range. I have a little motto that I use when engaging in potentially dangerous sporting endeavors: fun and adventure not death and destruction.
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