uniforming primer pockets?

[Curt]

Actually the chamber is tight enough that fired case's are just above Min. size on my Wilson case gauge.By M4's fired case's are a hair above the max. line fired.

[MEHavey]

The only other option might be that the "...bolt is setting back..." under firing pressure and creating headspace. But your primer-only test would contradict that as the problem.

OK... Anyone else have any idea where the primer's finding room to move so dramatically backward -- in a (head)space that has no such room -- even when fired with no main charge?

[Mudcat]

I would imagine that you made it as far as you have by shooting instead of spending time uniforming primer pockets. I would further speculate that luck did indeed play a part, albeit a minor one. As to how serious you are about the sport, based on what I have read of what you have posted in the past, I would regard you as devoted to it.
Last, I don't know you.

Heehee...I was just messin. To be honest, I did actually uniform my first primer pockets about 2 weeks ago at the insistence of a fellow HP shooter as we were processing brass in his workshop. THe pockets look nice, the primers seat in deep, and with at least one of them I tried to fire this past weekend at a LR match, apparently seated too deep and didnt get a good firing pin strike. Also had 10 ring or more elevation issues with that ammo and cases...but, it was a new load so I am not chalking it up to that...yet....but I do believe it cost me the win (3 pts out).

In any event, uniforming primer pockets isnt a bad idea, probably a good one, but I do not believe its anywhere near necessary or required. FOr me, its too much time and effort that I dont have and I would rather spend the time I do have pulling the trigger.....more fun!

John

[Maury Krupp]

"Required?"

To make ammo that will hold the 10-ring? No.

I know enough shooters like John who can dump fired cases in the hopper at one end, pull the handle, then go shoot match winning scores with the ammo that comes out the other end.

To prevent slamfires? It doesn't hurt.

But preventing slamfires has so many components that to isolate one probably oversimplifies things.

I use a Sinclair uniformer to clean the pocket as a routine part of case prep. It's quick and easy and makes me feel more confident in the safety of my ammo.

Maury

[Parashooter]

The only other option might be that the "...bolt is setting back..." under firing pressure and creating headspace. But your primer-only test would contradict that as the problem.

OK... Anyone else have any idea where the primer's finding room to move so dramatically backward -- in a (head)space that has no such room -- even when fired with no main charge?

There are several other possibilities -

1. The bolt has sufficient forward clearance to allow it to force the case farther into the chamber when the bolt is closed forcefully.

2. The detonating primer itself can push the case deeper into the chamber.

3. Curt states "I am bumping the shoulder back about .003." Depending on where and how this is measured, actual end-play when chambered may be significantly different.


Sizer die and chamber slope may vary, leading to variation in end-play of chambered cartridge.

These effects may be cumulative, giving the effect Curt describes - although probably not really "backed out almost completely", which would be an extreme case. A small rifle primer cup is .110" high. If there were that much end-play, the firing pin (which normally protrudes about .050" at most) wouldn't be able to reach the primer to set it off - and the case would remain in the chamber since the extractor wouldn't be engaged with the case rim.

[MEHavey]

Curt,

1. Pull the extractor off the bolt and reassemble the rifle.

2. Try the "primer-only" test again -- a half-dozen cases.

3. See if the primers will still go and/or examine primer indentation when the case is not held to the bolt face.




.

[MEHavey]

The other thing to look at is the flash hole. As parashooter notes, the primer charge is trying to push the case forward in its own way and itself backward no less that the main charge tries to push the bullet forward and the case backward. Any room to move left between the case and the chamber will be found out by this action/reaction, and will be exacerbated by an undersized flash hole.



.

[Curt]

OK had a busy wil try that after work tomorrow thanks.

[John Kepler]

I put a primed case in my rifle yesterday to test a new firing pin, I placed the muzzle against a folded towel on the floor as to not scare the dog and the primer backed out almost completely.

From an old R&D "Lab-Rat": Sometimes, bad indicators are giving you a window into the "real world"....other times, a bad testing design telegraphs the flaws in that testing system rather than ANYTHING going on in "the real world". In the case above, you have an absolute primer in the later rather than the former!

To begin, in the situation articulated, I'd be VERY surprised if I did NOT get the results you did with PERFECTLY seated primers! You've set up a situation where the primed case will generate enough bore-pressure to slightly open the bolt, but not enough to pressure-seat the primer. The result is a pushed primer each and EVERY time! You MAY have a primer-pocket issue....but that test doesn't prove or disprove the theory!

[John Kepler]

"Required?"

To make ammo that will hold the 10-ring? No.

I use a Sinclair uniformer to clean the pocket as a routine part of case prep. It's quick and easy and makes me feel more confident in the safety of my ammo.

Maury

DITTO!

I've got a Sinclair pocket-cutter myself.....it's in the drawer with the "other" loading/case prep gizmos that turned out to be solutions searching for a problem to solve! I quit using it when I noticed that if I cleaned the primer pockets with an RCBS pocket cleaning brush before I used the Sinclair pocket uniformer....the cutter didn't do anything, didn't cut a speck of brass out of any of the cases I used! Since the RCBS brush was easier and faster to use, the expensive Sinclair tool hit the Loading Bench Black-Hole, eliminating another potential variable out of my loading system!