uniforming primer pockets?

[Parashooter]

Sometimes when what I'm seeing posted on these forums doesn't make sense to me, I have to try it myself as a kind of sanity check.



When I fired the normal case, I pressed my rifle's bare muzzle (no flash hider) against a folded towed and watched for any bolt carrier movement. Nothing, zero, nada - even with the magnum-strength CCI 450. Considering that the carrier would have to retract at least 1/8" before the bolt even started to rotate, it seems highly unlikely a primer would produce enough volume of gas to cause unlocking. There must be another explanation for the phenomena described in earlier posts on this thread.

My guess is that the extreme primer protrusion Curt described was from a loose primer (undersize cap or expanded pocket) that moved back during ejection - a result not of pressure but simply inertia. That's something I have seen, especially with military cases where a trace of the annular crimp remains to catch the front edge of the primer cup and keep it from falling out completely. Primers found in this condition can often be pushed back into the pocket with little effort, demonstrating that they are not tightly fitted.

[MEHavey]

JK
... >
... > The "dog" in my case was the wife....
... >


Ooooooohhhh..... Have you discussed this comparison with your dog?


.

[Curt]

I'll be honest with you I don't know if the bolt moved.The barrel is a Lillja Service rifle barrel from a blank, No muzzle device. I was most surprised that the towel I used had a nickel sized melted burn mark on it when I was done. I slowly ejected the case out on the floor and when I picked it up I noticed the primer back out, just hanging on by a thread. The rifle was built by a pro NM builder and was close to 2K. I don't remember any specifics about the chamber this was my first leap into the AR, my M1A is shot out and I asked for a rifle that was the best of the best as I am getting serious about working towards a Distingshed Badge.
I was using a Stoney Point case headspace tool and pushing the shoulder back .003 with a F/L Forester die. I have measured new S&B rounds out of the box and they are about .004 shorter than my fired case's.
A friend is dropping off a few once fired LC case's and CCI primers and I will test on Saturday to see if this fixes my problem. I think It is going to come down to the primers.
Up until now I have only loaded 308, and enough of it to burn up a M1A barrel and never ever had any problems with brass or primers.

[MEHavey]

This happens on *both* R-P and Win brass?
I gotta tell'ya, Curt, You've done everything I can think of other than to:

- Just *not size at all* a coupla cases already fired (full pressure) out of *that* rifle,

- Re-prime/re-chamber and manually check/ensure lockup,

- See if it still pops the primers back out.






.

[Curt]

Talked to Sierra ballistics and hit the range with a variety of loads, primers and brass.As long as I stay about a full grain under max loads primers stay put and show acceptable amounts of pressure.
Tech. I talked to believes that a tight barrel and chamber on the tight side may be the culprit, the barrel may loosen up a little over the season. I guess when my backordered chrongraph shows up I will get the whole story. The rifle shot some little tiny groups too. I feel a little better.

[MEHavey]

What you're experiencing intrigues me, as most overpressure loads flatten the primer up tight against the case head, ... not pop them out of the case.

It almost seems like it's a residual pressure thing where the bolt unlocks and starts to open while high(er) chamber pressure remains -- and that pressure then finds sufficient space to back the primer out into the extra headspace created by the opening bolt.

Ever consider a possible timing/gas port problem?

[Curt]

Well the ones that don't fall out are flattened against the case head.Not horrible, not flowing, no sign of gas leakage, no sign of bolt face print on the case head. When I initially worked the load up that is where I stopped and backed down a little. Then I fired the last match of the season with last year and I picked up quite a bit of brass with no primers.Of the 60 rounds I fired Sat. I lost no primers. I would like to sse how fast these are going compared to my Sierra manual before I make any other assumptions or problems for myself.

[MEHavey]

Did that M2 come in yet ?

[Curt]

backorder till may 5th., I just found out my buddy has a shooting Chrony he has been hiding for a few years, if it ever stops raining I will run that to the range and get some numbers.