Extruded primers?

[Jasper1573]

Today I met my Dad at the range to zero in a new scope on his .243 Win. Dad brought a long time friend with him who was shooting a newly acquired 1970s Remington semi-auto in 30-06 cal. I think it was a Rem 7400.

After shooting about a dozen rounds through the 30-06, I was looking at the brass and noticed that most if not all of the primers had been pushed out of the primer pocket a small amount, just enough to make it noticeable. But one of the primers was literally pushed half the depth of the primer out of the primer pocket, say about 3/64 of an inch, something just short of 1/8 of an inch.

This was factory Winchester Super-X ammunition. If this were a handload/reload, I could find some reasons like overpressure, loose primer pockets, etc.

What would cause factory ammunition to push the primer out of the back of the brass case?

Jasper

 

[THplanes]

Have the head-spacing checked. It could also be bad ammo that has the shoulder set too far back. This would in effect give you a head-space problem.

 

[bigedp51]

I found this, your question intrigued me so I got curious because my 760 would open or unlock by itself after years of shooting. The cure for this was to change the bolt locking threads from right hand to left hand threads to keep them from unlocking under pressure. If your Remington is cycling the bolt too soon (gas system operation) this could cause the primers to back out as the bolt opens.

Remington 740 Gas nozzle size

Does any one have any information on the size of the inside diameter of the gas nozzle for a Remington 740 semi-auto 30.06? The Gun is opening too soon causing the extractor to disengage from the cartridge leaving it in the chamber after being fired. I need to make sure the nozzle isnt too large and allowing too much gas into the inertia sleeve too soon.
Any information would be of great help.


The 740-742-7400 series ALL tend to unlock when chamber pressure is a bit above that of most other semiautos. Just stand behind and to the right of one fired around dusk, and you'll see flame coming out of the ejection port. This causes the deposit of residue in the chambers.

Your 740 is also a pretty old gun... so check the action spring. If it's never been changed out, it has probably shortened significantly, and most likely has also corroded, since it sits right where it will collect residue from the gas system. A weak spring will also cause premature unlocking. Change the spring...

Lastly, this is from a retired Remington service rep, told to me many years ago: The service department recognized this problem, but the engineering dept refused to rework the design. So his recommended, but "unofficial" workaround was to drill the gas hole (the one the "nozzle" fits in) in the inertia block a bit deeper: .750" deep (using drill stop collar) with No.3 drill. This retards the gas system a bit, but doesn't affect reliability... the same amount of gas is used, just a bit later in the cycle, when the chamber pressure has dropped.. he said this really helped, but I never had occasion to try it myself, although it makes sense.

http://www.practicalmachinist.com/vb/gunsmithing/remington-740-gas-nozzle-size-127513/

 

[ArchAngelCD]

I agree, it sounds like a head space problem.

 

[Walkalong]

Light loads will do that as well, but since it is factory ammo.......

 

[Jasper1573]

One other bit of info that I left out...the rifle failed to eject every round that we put into it so we had to single feed it. Could the ejection problem have anything to do with the primer issue?

 

[bigedp51]

Jasper1573

READ this very slowly.

You had primers that backed out of the primer pocket and you also had these primers protruding at different lengths.

The gas system of this rifle is NOT working properly, and the bolt is moving when it should NOT be moving. This bolt movement is what is causing the primers to back out under chamber pressure.

Dissemble the rifle, clean the rifle and inspect the rifle for, damage, worn parts and function.

Again the gas system on this rifle is NOT cycling the bolt properly and its operation is FUBAR.

Low pressure can cause the primers to protrude and not be "pushed" back into the primer pocket. (headspacing on the primer)



Below what happens during the firing cycle of the cartridge in a rifle with long headspace. Please watch the primer move in relation to the case and bolt face.



If you study the above image and think about what your rifle is doing you will see your bolt is moving and the primer is not being reseated. Your bolt is moving to the rear when it should be in the locked position.

The bolt of your rifle is moving when chamber pressure is still pushing on the primer and the primers are being "unseated". If this problem gets worse your rifle will be able to vent 58,000 cup of chamber pressure and this might ruin your day.

 

[Jasper1573]

Rifle is currently a reputable gunsmith...I will pass along the info.

Thanks