Tight primer pockets

[drumcorpschamp]

All,

Just finished prepping a fresh batch of Lapua "blue box" .260 Remington brass. Thought I'd load 15 rounds with my competition load and see how they shoot, hoping they'll do well and I'll just fire form at my next two matches. So far, so good.....right?

All of these 15 cases took A LOT of pressure to seat the primers. I couldn't seat the primers to contact the bottom of the pocket with one hand. In fact, some of these seated primers started to flatten a little from the seating pressure.

I am using a K&M hand priming tool which has worked great for me. The last fresh batch of brass primed much easier at the initial loading and loosened up just a little at the first firing.

On this new brass, the inside diameter of the primer pockets measure an average of .2085" with a Mitutoyo digital caliper. The O.D. of the Federal 210M primers measure an average of .2108".

I have no idea what the size and tolerances are supposed to be for the brass and the primers, but these primer pockets on this batch of brass are obviously smaller than the last batch. I can measure the pocket diameters more accurately than with a digital caliper, but feel that moot as it takes two hands to get the primers seated. Just too tight!

Anybody have similar experiences? If so, how did things work out for you?

I have a lot of time in this brass getting it prepared would prefer not to scrap the batch. I did finish loading these 15 cases and hope that upon firing, they'll loosen and seating primers will go easier. Keeping my fingers crossed.

Thanks,
Jerry

 

[Killshot]

I believe the tolerance for the pocket dimension is .2085" to .2100".
Here's a list of the various Large Rifle primer's diameter:

It appears those Federal 210s are the fattest.


Maybe just do this a few hundred times a day.

Tight primer pockets are a good thing!

Seriously, though, good luck with your issue.

 

[tonedaddy]

I had a problem with any Lapua brass and Rem 7 1/2. Switched to Federal 205m no more problem.

 

[Shynloco]

I use the Sinclair Primer Pocket cleaner even on new piece of Lapua brass and on every reloading thereafter. Works for me and I have none of the hard seating issues you mention whether it's on my 6.5, 6mm, 223 or any of the other calibers I reload for.

 

[drumcorpschamp]

Thanks for the input guys.

Dave...I won't be at Mayberry this Saturday and have a couple home projects that may keep me away from the shoots for a few weeks. I'll give priming a whirl in my Lee press. Don't have a fancy strip setup, but I think it should work ok for me. Appreciate the offer and I'll get them to you if I get in trouble!!

The new 6BR brass seats the primers tough as well, but not as hard as the .260 brass. Didn't turn the necks on them. Looks like they'll work great.

Be well,
Jerry

 

[BoydAllen]

A couple of thoughts:

A caliper is not an accurate way to measure the ID of a hole.

Was the resistance felt as the primers were first started in the pockets, or was the problem with getting them to full depth, toward the bottom of the pocket. The reason that I ask is that years back, when I first started loading Lapua .220 Russian brass, for my 6PPC, I had the same problem, with Federal primers. It turned out that the problem wasn't the diameter of the pocket or primer, but an overly large radius at the bottom corner of the pockets. This had been a common enough problem with that brass, that one of the suppliers, that caters to benchrest, Russ Haydon, offers a tool that is specifically designed to cut out the offending material. Previous to getting that tool, I had tried my Sinclair primer pocked uniformer, and found that because it was not designed to cut on its sides, that is would jam the bottom of the pockets, which had a slight taper. I don not know if Russ offers the tool in a large primer version.

Another issue, that has been reported with the .220 Russian Lapua brass (that I have not experienced, but which may be a batch to batch variation) is pocket tightening caused by new brass having slightly convex heads. In this case, firing flattened the head, while simultaneously tightening the pockets. Using a Wilson case trimmer to flatten the heads of new cases solved that problem. (if I remember correctly) Not having examined your cases, I have no idea if either of these issues might be the cause, but I thought they were worth mentioning.

I should add that I have large strong hands, and that the force that I applied (before I got the Haydon tool),trying to get primers to seat below flush, deformed primers to a degree that was easily seen.