Primers backing out after firing???

[De41mag]

I've got a Ruger Mod 77 MKII in 7.62X39, been shooting the Soviet stuff for about a year. Lately the Soviet stuff has been CRAP. So went to the American stuff, much better accuracy. BUT....
Firing these rounds, I've noticed that the primers are backing out above the base of the case, and it only does it with cases with large rifle primers.
I've not reloaded for this case yet and don't know if I will. But with Federal, Winchester, and PMC that use large rifle primers they are backing out. Now Remington, that uses a small rifle primer this does not happen.
I've noticed that the American rounds seem less in recoil and power, so I know the Soviet stluff is plenty powerful and the primers don't back out.
Been reloading for 19 years and never seen this happen.
Any input, would greatly appreaciated. Thanks.  :grin:

Dennis  

[jhalcott]

It's possible the heavier soviet stuff is "backing up"onto the primer.When the wimpy US ammo goes off it stays forward in the chamber. Giving the primer room to move .

[Flash]

Measure the distance between the case rim and the shoulder on both of the unfired brands of ammo. They might be slightly different or the steel cases might have a thicker coating of lacquer, changing the headspace.

[New Hampshire]

It may just be me, but Ive yet to find a .30/30 that did not have a backed out primer in a spent case.  I believe this is common with lower pressure rounds.
Brian .

[tony212]

New Hampshire....funny you should mention the 30-30. I was just about to say every case I shoot in both my 30-30s have the primers backed out.  Even with factory ammo.
tony212

[Iowegan]

Many shooters think a backed out primer means too much pressure when it's really the opposite. The primer is forced out just from the primer mix. Pressure pushes the case back and reseats the primer.

Try this trick with most any gun. Fire a case with just a primer ... no bullet, no powder. In nearly all cases, the primer will back out considerably.

[De41mag]

MANY THANKS FELLAS!!!!  

I kind of figured it was not high pressure due to the lighter recoil of the American Ammo. But I was thinking along the lines of a headspace problem, but the accuracy was excellent. Still saving all the brass, but in limbo about reloading for it.
Again thanks for help Iowegn, tony212, New Hampshire, flash, and jhalcott.

Dennis  :grin:

[bob helget]

I experienced the same problem of primers backing out of the case when working up loads for my 7-30.  As i worked up the loads to more powder I started to get primers backing out.  I too thought I had too much pressure.  I bought two boxes of factory loads and these also backed out.  The advise I received from this forum was a headspacing problem.  After readjusting the dies I have had no primers back out on my reloads.