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I have done incremental work ups in 9mm to see what happens with many bullets and powders.
1) The feed ramp of most 9mm pistols intrudes ~.190"
The web of most 9mm cases is ~.160"
This leaves ~.030" of thin unsupported case wall.
That is not a problem for SAAMI loads or even +P+, but with enough powder the limit can be reached.
2) Another problem is the rimless case may expand at the extractor groove and the primer fall out.
3) If the first two problems don't stop me, sometimes I get a pierced primer and want to go higher. The small magnum pistol primers are made from thicker brass [no, the brass is not harder].
When I go to the magnum primer, I must start over ~.7 gr. less powder that where I left off with the standard primer. Then with ~.3 gr. more powder [plus extra primer power] the magnum primer starts piercing.
4) The small rifle primer is the same height and diameter as small pistol primers, and does not have the dimensional differences like large rifle and pistols primers.
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