Primer backing out.

I had shot some Federal Power Shok ammo through my Marlin 336 and I noticed that the primers were backed out a bit. All 16 cases had primers that were backed out .006-.009". I need to go shoot some Remington ammo through it and see if I get the same results. If I take the fired case with the backed out primer in the chamber then run the bolt all the way forward the case will not extract because the extractor is unable to get to the edge of the rim of the case. What do yall think? Sound like a possible head space issue more then just under powered ammo?

I did find this article. It says that rim headspace for .30-30 is .063"min and .070" max.

http://www.castbullet.com/misc/hspace.htm

The rims on my fired ammo seem to measure .059 + .006-.009" for the primer. So maybe the headspace on my gun is not over spec and the rims of the factory ammo are under spec just like they do with bottle neck cartridges.

isn't primers backing out also a sign pressures being too low?

I was going to say that it could be 2 things head space , or low pressure. or both. but looks like you have your own answer. if the ammo is under spec its still head space just not caused by your rifle.

I think if they mike as you say I would contact the ammunition MFR and request a replacement.

Yeah low pressure will back them out as well. I think my gun is on the max side of head space.

I ordered a bolt locking lug to replace the old one. It might require some fitting but hopefully it will tighten up the headspace some. I will become a Marlin expert if I have to do keep doing work on this rifle.

I have a similar problem when firing mil surp 5.56 ammo in my 14" .223 T/C Contender barrel.

I was told that it is a sign of overpressure because of the difference in throat length and shape between the 5.56 and .223 civvy.

This fellow: http://www.m-guns.com/tools.php

Makes a throat reamer specifically to ream short .223 throats to longer 5.56. This drops the pressure and prevents the primers from popping out.

I am still waiting on my reamer and gauge with an eye to ream my AR-15s, and T/C .223 barrels.

RemMan700 wrote:I ordered a bolt locking lug to replace the old one. It might require some fitting but hopefully it will tighten up the headspace some. I will become a Marlin expert if I have to do keep doing work on this rifle.

I sent my 336 back for a refund. 3 times back to Marlin/Remington for work on crown, barrel, ect. with the same crappy results at the range was enough for me. A guy shouldn't have to become an expert in order to get flawless action from a rifle. That's why I'm a Savage convert now, deadly accurate right out of the box with no performance flaws of any kind. Although, I will say that the older Marlins of days gone by like around the 70's era are some fine lever actions. My brother has been using the same Marlin 336 in .35 Remington since he was 13, he's now 45 and still carries it every year in deer season. His Marlin is very accurate and never given one ounce of problem whatsoever. I know that doesn't have anything to do with your original question, just wanted to offer my experience with the newer Marlin rifles of today.
Good luck with it, hope you can get the problem fixed.