Primer Seating Depth

My last couple of small batches of .243 Win loads have been coming out with primers either flush or slightly protruding. I'm full-length resizing Remington Brass with WLR primers, the same combination I have been using for about 15 years. In the past, the primers have always come out slightly recessed (never actually measured.) I'm seating the primers with the primer arm of my RCBS Rockchucker. I replaced the primer arm a couple of years ago and it has been working fine up until now. I cleaned and reassembled; no change. It occurred to me that the primer arm post may simply not be pushing the primer in far enough for some reason, so I unscrewed it to make it longer, a little at a time, and still had no improvement. The height of the primers I am using is 0.125"; another box of unopened primers is 0.130"; spec is 0.128"+/-. Of the last two batches, one was once-fired brass and one was 8-times fired brass. I have never cleaned primer pockets in nearly 40 years of reloading. I have a Lee hand-priming tool, but prefer the Rockchucker. Any thoughts/ suggestions?

I would check the lee to isolate the problem first. If it’s seating them flush then you know to look to the rockchucker for the issue. Since it wasn’t all the same brass I’d say you can eliminate that.

papa.....have you tried other primers using the same methods? Reason I ask is that very recently I was loading Prime brass (Norma) using WLR primers, and I had a hackuva time getting them to seat flush. Some would, some wouldn't. I switched to CCI's and had no trouble at all. There were large batches of WLR primers that were giving people fits (well documented on 24 HCF), and after my experience I'm wondering about Winchester's quality control a little bit.

Never hurts to clean the primer pockets.

From a quick check the primers in the OP are within the +/- specs so that should not be a problem.

Pocket Type Depth Min Depth Max
Small Rifle 0.1170 0.1230
Large Rifle 0.1250 0.1320

Winchester primers have been the least consistent for me in diameter, height, and shooting (ES).

And, I have never NOT cleaned a primer pocket on a piece of brass.

papa45, first thing you have to do is clean out your primer pockets. After a few firings, there will certainly be build up that can cause issues with the consistency on your seating depth. Once you do this, you should see some consistency return.

But to answer your question, the primer specs is to seat the primer about .003"-.004" below flush, and not go deeper than .008" deep. The Win primers are sensitive on primer depth, and I keep them about .002"-.003" deep.

Other than tumbling in corn cob media I have also never cleaned a primer pocket with no problems. I doubt if he has been loading for 40 years that all of a sudden its cleaning the primer pocket.

I would try the hand primer, I didn't like the press mounted primer and have always used the RCBS hand primer. Has anything else changed like shell holder?

I'll shoot a round maybe twice without cleaning a primer pocket. But after 3-4 firings without cleaning a primer pocket, you will have a build up of carbon and primer compound. If you do not remove this, it will certainly interfere with the primer seating depth. We are talking thousandths of an inch, so yes, this would be the first thing I would do. Then see how the primer seats.

Thanks for all the input. It's hard to imagine that after all these years, primer pocket cleaning is suddenly a problem, but I will try that to see if it makes a difference. I will also try seating a few with the hand primer. The shell holder has not changed. Unfortunately, all my empty brass has been primed, so I will have to wait a little while to check out these suggestions.

The ONLY thing that might be different is that I have been testing a new powder with some of that brass. I suppose the chemistry and residue after firing could be different, but...inside the primer pocket?

I'm still betting on WLR primers being the problem.

I wouldn't think so. Every time I've had any burn get inside the primer pocket, and leak around the primer was a hot load (and or wet weather), and the brass was smoked, meaning primer pocket would not be reliable, or would not hold a new primer at all.

I'm leaning on dirty pockets as well as the Win LR primers. I seem to remember a chart Chad posted, that showed Win LR primers being the narrowest diameter of all of them. That contributes to them coming out of some of my 3X fired Federal .308 brass, which has poor primer pockets to begin with.

When I first started loading the 30-30 with a LEE hand loader i had some primers not seating well after 3 to 4 loadings before cleaning the primer pockets. I cleaned them with a small flat blade screw driver scraping the crud out of the pocket. It worked then and have cleaned ever since

OK, I couldn't wait. I went to the range and shot up some ammo, just so I could check out your suggestions. I shot from three different batches; (1) a bit older with primers slightly recessed, (2) with raised primers, and (3) with primers "crushed down" to flat. I was a little afraid of (2) for obvious reasons and I was concerned that I might have damaged primers in (3) and they might not fire or give me a hang-fire. All three batches fired the same (consistent velocities and POI's) with no apparent problems.

I prepared the brass in my normal way, adding a step to clean the primer pockets. The primers all seated with much less pressure than I had become used to. I used only WLR primers. About a third of them were done with the hand primer, with the same results. All primers came out recessed from 0.002" to 0.006". I can probably get the seating depths more consistent as I develop a feel for the cleaner primer pockets.

I still don't know why this suddenly became a problem, but, obviously, old dogs can still learn new tricks. Thanks for all your help.

Welcome! I was certain it was the debris in the primer pockets causing your issue.

Perhaps tumbling in corn cob media cleans them more than I give credit.

Primer pocket brush in a drill press, makes cleaning primer pockets a snap. I will not decap and then vibratory clean. Media will get in the flash hole, on many pieces, requiring inspection of every piece.

Fireman, the de capping pin in your die will punch it out of the flash hole.

Very true.

I believe it is faster to remove one more throw of the press, and add the brush in the drill press step. Meaning, I'd rather not decap, clean, and then size anyway. I've not seen the pockets get what I call "clean" in a vibratory tumbler. The brush in the press makes the primer pocket shiny brass, in just a couple of seconds. So I would remove any media prior to the brush anyway.

In the event of stainless tumbling range pick up brass, I will decap, then tumble. The stainless media, water, Dawn, and Lemi-Shine sure enough get the primer pockets clean.

FWIW, corn Cobb media in a vibratory tumbler is what I use and it alone does not suit me either. I hit the primer pockets with a wire brush on my RCBS case prep center before they go in the tumbler.