Seating Primers

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gunboat57

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I've been reloading for years now and this question never came up before:

According to SAAMI specs a large pistol primer can be as tall as .125" and the primer pocket as shallow as .117". What happens to the primer if it's fully seated and protruding but you push harder to get it even?

I just seated a .120" primer in a .118" pocket. It was sticking up so I carefully used a cam press to press it in flush, just to see what would happen. It didn't go off.

By doing this does the primer get damaged in some way? Anyone ever set off a primer by using too much force to get it even with the cartridge base?
 
Added information: the .120 primer that I pressed into the .118 pocket went off normally when fired in my 44 mag Redhawk.
 
There is the cup, and there is the anvil. There is some give in the anvils legs, so in a way, they are adjustable, up to a point of course.

They need to be seated at least flush, and below flush is much better. Do not be afraid to seat a primer hard.
 
Most primers work fine even after they've been crushed a little. When I first started reloading, I was paranoid about not seating deep enough, and I made hundreds, if not thousands, of rounds of ammo with visibly flattened primer cups. Using CCI primers, they all went off.

Common wisdom is that crushing a primer a little can "presensitize" it, making it more likely to slamfire.

Also, common wisdom is that if a primer is crushed too far, it may not go off for w/e reason. I can't be certain, but I think this may have happened to me a couple times using Tulammo primers. Dunno. Stopped buying them.

Benchrest rifle shooters believe that crushing a primer can affect accuracy.
 
Benchrest rifle shooters believe that crushing a primer can affect accuracy.
Click to expand...
We were talking primers one day, and Allen Hall told me if your primer goes off, you don't have a problem. Allen is in the benchrest hall of fame, and the maker of Hall actions by the way. Most of the older shooters agreed. We still tried to seat the primers the same every time, but that is different entirely. Some liked to seat em soft, and some liked to seat em medium, and some liked to seat em hard, but most everyone agreed that seating them consistently was the most important thing.

It is terribly hard to crush a primer to the point of ruining it.

I also do not believe seating one hard will "presensitize" it. It would be interesting to see actual tests.
 
I believe it.

Early in my .223 reloading, I used my Rock-Crusher press to smash primers in GI brass that I had failed to remove all the GI crimp from.

My AR-15 would often double or sometimes tripple, or fire once when dropping the bolt on a loaded magazine.

I found that complete crimp removal and normal seating stopped all that foolishness.

I just seated a .120" primer in a .118" pocket.
Click to expand...
As noted, you can't measure a new primer before it has been seated.
Because the anvil is standing proud above the actual cup by as much as .010" or so as it comes out of the packaging.

Only after seating is the anvil pushed into the primer compound to pre-load it.

rc
 
As long as there is no primer cup above the base of the head you should be good to go. I prefer to seat then .003 below flush if they will go but they all worked for me if not in that far anyway. In 40+ years of reloading I never have yet set a primer off by mistake while priming brass. Not even with them sideways and having to crush them to get the brass out of the Lee hand primer. IMHO if you go slow and easy there should be no problem with that. Once for an experiment I crushed one in my vise till it was FLAT and it did not go off. I often wonder what others do to set primers off due to my experience.:confused: YMMV
 
Rcmodel and walkalong, what you said is news to me but when I think about it, it makes perfect sense. I always thought the anvil was already in contact with the priming compound before you seated the primer. But I guess that would make the primers too dangerous to handle or you'd get slam fires.
So really the anvil has enough "compressibilty" to allow for the overlapping tolerances of the primer and the pocket.
One problem I have is my press doesn't give me enough leverage to seat the primers flush for some of the brass I reload. So I'm using a cam press and dowel to do the final seating.
 
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gunboat57 said:
One problem I have is my press doesn't give me enough leverage to seat the primers flush for some of the brass I reload. So I'm using a cam press and dowel to do the final seating.

It's a Lee Classic single stage.
Click to expand...

The Lee Classic single stage press provides incredible leverage because of it's very heavy linkage. Something else must be causing your seating problems because I'm sure it's not the Lee Classic SS press. Are you sure you're not trying to seat primers in brass with unprocessed crimped primer pockets? That would be a problem for any press, even a press meant for loading 50 BMG ammo.
 
I do not yet reload but based on my research so far, would it help any to use a primer pocket 'uniformer'? The tools as I understand them have blades that cut / shape the primer pocket. Would it be able to trim the pocket just a little deeper to make a little more room for the primer so that it doesn't crush quite so far?
 
ArchangelCD, I'm going to check my press over to see if there's something hanging up somewhere.

Most of my brass is new and has not been crimped. I have no trouble seating primers to the point where the anvil has bottomed and the primer is still sticking up a few thousandths. That's when seating to the flush condition gets hard. Maybe I've just been too cautious.
 
A primer pocket uniformer cuts the bottom of the pocket square, as well as cutting them all to the same depth.

A flash hole uniformer removes any "hanging chads" from the inside of the flash hole, as well as making the diameter the same on them.
 
OK, I found the problem and the solution.

Are you ready for this?

The toggle levers of my press are bottoming out exactly when the primer is .003 above the base of the brass. Higgite, you got me thinking when you mentioned the shell holder. The only way the shell holder could cause a problem is if it positions the base of the brass too high for the primer arm to seat the primer. That's exactly what was happening.

My high-tech solution is to lay a popsickle stick under the side arm of the primer arm so it rises up well before the linkages bottom out. Now I'm consistantly seating primers about .003 below the base regardless of how tall the primers are or how shallow the pockets are.

Many thanks to all who helped educate me on the fine points of primerology and find the problem.:D

LeePress.jpg
 
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I'm aware that this isn't the O.P's problem since he's using brass without military crimps, but it could be useful to some to know about....

A couple of years ago, I made my first reloads to shoot out of my new Remington R25. This was very old (1967) 7.62x51 LC brass, that came off a National Guard small arms range. given me, and kept in my garage for 40 years. (Never owned a .308 before the R25). I had trouble swaging that stuff. Some swaged ok, some had to be swaged twice, and on some, the swager simply sheared a little ring of brass into the bottom of the pocket. Had I been using my Rock Chucker I would have caught any high primers, but I wasn't. I used my Pro 2000 with a brand new .308 tool head.

Anyway, long story short, I had two high primers I didn't catch until the reloading (of 50 rounds) was done, and I was ready to shoot the rifle at a range. I didn't pay serious attention to them, thinking so what...most likely nothing's going to happen.

Well it did, first try. I loaded up a magazine. First high primer was the third one from the top. Bam............BamBam. I was glad it was on a bench rest, but it's still a bit unnerving....and more than a bit embarrassing.

Anyway. I put that last shot case in my pocket, and did the same with the other unshot high primer round, and shot the rest with no problems.

Back at the loading bench I pulled the bullet on the unshot round and deprimed both rounds. A sliver (tiny ring) of brass dropped out with the two primers. That's when I realized what was happening. I started uniforming pockets after that, and that helped the Pro 2000 to seat the same on each round using the built-in ram stop on the press. However.....when the swager would shear a ring into the pocket, the uniformer would just spin, and not cut into the pocket depth. That's when I decided to ream the rest of that old hard batch of brass.

I'm a believer in uniforming brass, especially if you load on a progressive. IME, factory pocket depth varies too much.
 
Presses that are not securely anchored to a solid bench can cause problems with high primer seating. But if a popsicle stick works for you, go for it.

gunboat57 said:
OK, I found the problem and the solution.
LeePress.jpg
Click to expand...
 
I had a similar issue several years ago.
I had gunk (case lube, dust, tumbling media, carbon, etc) built up in the shell holder.
So it was holding the case up too high.
A good cleaning on the channel around the inside of the shell holder fixed it.
 
Otto, as you could tell I've got my press bolted to a plank that I clamp to my reloading bench. That way it's portable. It does make it a little springy. But when I seat primers I put my left hand on the press and my right hand on the lever and squeeze them together. After a long reloading session you can feel it in your pectorals.

I just think its amazing that all the dimensions of the rim, shell holder, ram height, and toggle levers came together to keep me .003 short from fully seating my 44 mag primers. I've had no trouble with 357 mag, 30-06, 8X57, 45 Colt, and several others. But I realized that my 303 Brit has the same problem with primer seating and needs the popsickle stick modification. Weird.
 
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ArchAngelCD
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Join Date: November 25, 2006
Location: PA, USA
Posts: 11,825
IMO for general use a primer pocket uniformer does not aid in seating the primers. they do make the pockets the same so the flash is the same for benchrest shooting.

I have never used a uniformer, I just clean out the pockets with a cleaning tool, RCBS mostly but the Lee primer pocket cleaner is cheap and it works.
Click to expand...

The ONLY purpose of a primer pocket uniformer is to facilitate seating...has nothing to do with consistent flash. A flash hole reamer, however, ostensibly does help with flash consistency.
 
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