So, because I'm determined and/or stubborn, I have gone and done this.....
I made a tool, for counter sinking around the primer pocket on the inside of my brass shells. Now I'm not professional tool maker, and I just used a piece of an axle shaft from a 1988 Toyota 4 Runner, so it looks a little crude.
But it seems to work, even after I broke a tooth off.
25/32" outside and 1/2" centre hole. I could probably go with something smaller, like 0.400" centre and still have quite a bit of material left around the primer.
The head of the shell (well, stubby practice piece) ended up being about 0.110" thick.
Then out of curiosity I made a tool that could do this to the end of a bass shell:
Is it safe to close brass shells this way instead of using glue to hold everything in??? My understanding is that they won't last as long as they will start to crack from being formed and reformed over and over again.
Unfortunately my tool also caused this (I was just messing around and using a bench vise):
Just for the record, it was a scrap shell. Didn't waste a good one to try this out.
I broke my priming tool a while ago. Then fixed it by welding it, and it broke again....
So I made my own, industrial strength!
Seems to work, could use some refinement. But for how many 10 gauge shells I reload each month, my slow process of priming and loading seems to work fine.
I'm open to input here. Is it even a good idea to countersink my shells like this? As in, the powder will have to burn back, but it seems that the old 10 gauge brass were made like this. I mostly wanted to do it so that the shells will fire-form more evenly. The ones I've tried that had a thicker head, they would bulge out noticeably where the material was thinner and leave a band unformed around the rim.