38 Super spent casing question: Primer doming

[BugI02]

Hi, all. I was preparing to reload some once fired (by me) Armscor brass (125gr) and noticed as I was depriming that the pressures had pushed out the dimple made by the firing pin, and in some cases slightly domed the aft face of the primer. This was factory ammo with a claimed 1215fps

I have not seen this before. They were fired from a full size 1911 with good case support and no bulging or other issues were seen on the cases

Any ideas on why this would happen at relatively modest pressures? I got a good deal on the ammo at a LGS and while it looked to have spent some time on the shelf, I wouldn't suspect it to be more than a couple of years old based on the wear/fade of the box

Anybody know of any issues with the factory Armscor components. Many of the primers were so smoothe they looked like they had not been fired at all

 

[Leadeye]

Never have seen that, over pressure usually makes the firing pin indentation look a little cratered and the primers look like they have muffin tops when punched out. I shoot a lot of 38 ACP in old guns and that's something new.

 

[red_zr24x4]

Were you looking at the primers after they were removed from the cases or before?
If after, the de-priming pin will sometimes remove the firing pin indent, sometimes it will dome a primer especially in a crimped primer pocket

 

[BugI02]

I was looking at the primers before depriming. Sorry I don't have any pictures as I just kept processing and got curious about this later. I did tumble the cases before depriming them (walnut husks)

I was intrigued because on a number of them there was really no visible firing pin mark. It was a perfect expansion of the dimple to leave the surface looking unblemished

 

[BugI02]

Update. Went and shot the reloads made with the armscor brass, slightly lighter loads booked at 130gr/1171fps (did not chrono) and nothing unusual about brass or primers(CCI) so I'm going to chalk this one up to whatever components Armscor was using in that batch of ammo (soft primers, maybe).

I've got some more armscor factory stuff to shoot yet and if it happens again I'll remember to get pictures. Will eventually be pushing to 130gr/1300 fps likely with VV3N37 (with a couple intermediate steps) so will keep an eye out for changes. Tempted to take a couple apart if it recurs and see if I can identify the components

 

[oldpink]

Update. Went and shot the reloads made with the armscor brass, slightly lighter loads booked at 130gr/1171fps (did not chrono) and nothing unusual about brass or primers(CCI) so I'm going to chalk this one up to whatever components Armscor was using in that batch of ammo (soft primers, maybe).

I've got some more armscor factory stuff to shoot yet and if it happens again I'll remember to get pictures. Will eventually be pushing to 130gr/1300 fps likely with VV3N37 (with a couple intermediate steps) so will keep an eye out for changes. Tempted to take a couple apart if it recurs and see if I can identify the components

Your guess about soft primers from Armscor sounds the most plausible.
As Leadeye already pointed out, over-pressure loads tend to do the opposite (cratering and/or flattening) to primers.
Cheap factory ammo, cheap components.
CCI's reputation is beyond all doubt, so you probably won't see that problem again, unless you shoot more of the same lot of that factory ammo.