Primer Seating Issue

[swede49]

Had a similar issue with Starline 32 H&R Mag new brass. Seems like primer pocket depths were not 100% consistent, and with an RCBS handheld universal primer, I had difficulty seating about 10-15% of primers, with some slightly deformed around the margin, but seated sufficiently well to fire in a Ruger New Model Single Six.

[fguffey]

I read one post on a national match shooter's forum once that said everyone knows brass gets longer and has to be trimmed, but few know the primer pockets become shallower with each firing.

It was like a slap in face to me because I'd been wondering why I couldn't get the primers to seat below flush on well used cases. I bought a uniformer and used a battery drill to fix them up.

One thing I realized though, the uniformer loads up with chips quickly and has to be cleared often. Don't try to muscle it, just back it out and let the chips fall free.

For years and years reloaders have read pressure based on the condition of the primer. Before the Internet reloaders used case head expansion. I have a flash hole gage. It measure the diameter of the flash hole, problem; if the reloader does not measure the diameter of the flash hole before firing he is wasting his time measuring after firing. After that it is a matter of being able to keep up with the flash hole, diameter of the primer pocket and diameter of the case head. If the flash hole increases in diameter, primer pocket also increases in diameter and then there is case head expansion. If the case head expands it shorten from the top of the cup above the web of the case to the case head. And then there is deductive reasoning; if the case head decreases in thickness why wouldn't the depth of the primer pocket decrease.

I have the RCBS case prep center with 5 positions; one of the positions has the primer pocket uniformer. It could be cleaning the primer pocket and it could keep the depth of the primer pocket uniform.

In the old days it was decided case head expansions was acceptable at .00025”. That did not mean after 5 firings the case head expanded .00125”.

F. Guffey

[PhillipM]

Thanks for that, F. Guffey!

[bigedp51]

I have a bunch of S&B .303 British brass that I have trouble seating primer in. About one out of five wind up just a bit high, not a huge problem in a bolt action but an irritant. This does not happen in any of the other brass I use (Remington, Winchester, Hornady/Frontier.) The press is a Rockchucker. Has anyone else had this problem with this brass?

All you need is a primer pocket uniformer and uniform all your primer pockets and you will have the same depth on all your brass.

Below a Hornady case prep trio and the uniformer is in the top position with the deburring tools in the bottom.

[fguffey]

I have the RCBS case prep center with 5 positions; one of the positions has the primer pocket uniformer. It could be cleaning the primer pocket and it could keep the depth of the primer pocket uniform.

Thanks for that,

You are welcome.

Remember; there is a chance the case did not start with the problem but developed the problem after being hammered with heavy loads. After that it gets complicated because of case head separation.

F. Guffey

[Merc]

I've been using PPU cases to reload .303 British. They're cheap and the new primers always fit properly. The PPU cases are heavier than most (especially Winchester and Remington) so they hold up well to multiple reloads as long as you neck size only and anneal the necks occasionally. Enfields are always tough on brass.

Merc

[fguffey]

I read one post on a national match shooter's forum once that said everyone knows brass gets longer and has to be trimmed, but few know the primer pockets become shallower with each firing.
.

And? That was it? They did not say anything else? They should have said the case head crushes when hammered with heavy loads; and then after that they should have said the case head increases in diameter and after that they should have said the flash hole increases in diameter. I always say "who knows?"; No one knows because no one measure before and again after.

And then there was a time I would ask what effect does all of this have on case head separation; I do not get answers, it seems it is not the question but the person asking the questions that gets all of the attention.

F. Guffey