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Old June 21, 2011, 01:11 AM   #4
HiBC
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Join Date: November 13, 2006
Posts: 3,815
I'll expand a bit on the headspace suggestion.When the firing pin hits the primer,the cartridge is driven forward.If there is space between the case head and the bolt face,the priomer will back out of the primer pocket till it hits the bolt.You might be able to see that by popping a prmed empty case in your rifle.When the powder ignites,and pressure goes up,the cartridge case head stretches back to the bolt face,and at this point,the primer gets flattened.
Now,sometimes a rifle has excessive headspace,which can cause all this.Real often,a reloader,in good faith,reads the die instructions that say to bump the shellholder against the base of the die.That is often not a good idea,as the tolerances of everything work out.The die will often set the shoulder back too far,creating a condition that resembles a rifle with excessive headspace.Its just a die adjustment problem.In a bolt gun,I like to get .002 shoulder setback from a case fired in that rifle.
There are tools and methods to measure this.There is a Hornady caliper attachment,there is an RCBS precision mic,and there are bushing case gages that can be used with calipers.Good luck!
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