I've been handloading amunition for 53 years now. Today, I ran into something I have never seen before. The cartridge is the .300 WSM. The brass has been loaded and shot twice doing load work up. yesterday I did a full length resize and ran them through the tumbler like I always do. Primer pockets were cleaned as usual. Then it was primer seating time. Pockets were still reasonably snug, but the primers would not go all the way in. I removed the offending primers and checked the depth of the primer pocket with my dial caliper. I then checked the depth one some once fired factory cases and with some new brass that was intended for the final handloads. Both were much deeper by almost .002".
During the firing of the test loads, there were no apparent signs of pressure, even at the manual's stated max load. velocity was good with a rather small ES, case head expansion was no different that factory and primers were nice and round with no sign of flattening. Yet, I believe they should have been extremely flat if it was excess pressure that pushed the floor of the primer pockets out by that amount. Even if it was defective brass that was too soft in the head, there should have been very flat primers.
FWIW, this occurred with every load from the starting load of 65.0 gr. of IMR-4831 to the max load of 69.0 gr. of IMR-4831 with the 150 gr. Nosler ballistic Tip. Load data is from the Nosler Manual.
I strongly suspect it may be high pressure but the lack of signs is puzzling.
Paul B.

Did you switch primers? Some are slightly diff. diameters. If you are running too hot, the pockets should be enlarging not getting smaller. The only other thing to check would be a burr inside the pocket.

Get a Sinclair primer pocket tool.

It's just a guess on my part, but what I believe you are witnessing soft brass experiencing flow. These short magnums are high pressure in their design. You probably just need to uniform the pockets, and they may need the process only once and reload fine for the remainder of their useful lives as the material work hardens.

If you mention the brand of brass you are using, others may be able to tell you of their experiences. If your velocities are higher than those cited in the loading manual, then you may have pressure issues.

Like Fred said it might be the primers. Rem LR's measure .209" OD and .123" high. CCI LR's are .211" and .126". It's not all that much, but .002" difference on the OD can definately be noticed when seating primers, especially with the Lee hand prime tool.

Thanks for the answers guys. I figured it out. The resized brass was a bit too snug so I adjusted the die to size them a but more. The expander plug was hitting the inside of the case just enough to push the bottom of the primer pocket out. The whole thing was my screwup.
Paul B.

quote:

Originally posted by Paul B:
... The expander plug was hitting the inside of the case just enough to push the bottom of the primer pocket out. The whole thing was my screwup. ...

Hey Paul, I see some minute amount of shortening in the Primer Pockets with typically standard calibers when I'm using SAFE MAX Loads. No doubt the Expander in your Die could have been shoving it back a bit, but you might still see it happen.

I've not reloaded any WSMs, so I can't comment on them being more prone to this or not. I do know they are intentionally designed with more material in the Case Head forward of the Extractor Groove, and that would tend to slow the Case Head Expansion slightly.

I use a Primer Pocket Uniformer as part of Case Prep. And I use it when removing Residue from a Fired case. By doing this, I get some indication of how much reduction is going on in the Primer Pockets by the amount of Brass removed as I clean them. This is simply another Pressure Indicator for me.

I would think that if you are still seeing a "measurable change"(using a Caliper) now that you have the Extractor readjusted, that you are in Pressure ranges (for those Cases) that I would not choose to be in.

Best of luck to you.