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.308 overpressure

nick89rs

Private
Minuteman
Feb 25, 2012
35
0
40
Maine
at the range today i had my first ever stuck case incident. Im running 44gr of IMR 4064 pushing a 175gr seirra HPBT the only factor i can imagine was that it was really cold today 35 degrees when i normally fire at 65-70 degrees. the first shot stuck and was difficult to extract. every shot after that was like butter no sticky bolt no flattened primers. was it just because the bore was cold or should i reconsider my load?
 
Re: .308 overpressure

Cold generally does not increase pressure. It decreases it.

If no other factors were present I would think case sizing would be the first thing to examine.

44gr of 4064 doesn't sound excessive.
 
Re: .308 overpressure

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: LoneWolfUSMC</div><div class="ubbcode-body">Cold generally does not increase pressure. It decreases it.

</div></div>

+ 1 !

maybe you had something in your chamber or in the lug areas... piece of cleaning cloth or something ?
 
Re: .308 overpressure

It did it twice more today after i made this post. First shot of a 5 shot string would stick. I know that lower temps make the pressure less i was more wondering if the cold would make the chamber smaller and when the brass expands it just dident have as much room? This is all pretty new to me so sorry if thats way off base. I FL sized all the brass could i have a setting misajusted on the die?
Thanks for the replys.
 
Re: .308 overpressure

You might be bumping the shoulder back to far. This might be causing gas to escape backwards. Do your necks have black soot on them? I would check this, your head space verses how much the shoulder is set back after fl sizing.
 
Re: .308 overpressure

Could be there's some grease/glue-like substance in the chamber and softens up when the chamber warms after a few shots. That explains why you don't experience sticky-bolt in subsequent shots.

Try wiping the bore and chamber with acetone or rubbing alcohol or simple green to start.

This is especially true if you've ever shot steel cased ammo out of that gun; steel casings are covered with a clear coat of some sort that tends to build up in the chamber.