Ammo length
What's important about the length, is not the absolute OAL, but how the cartridge rides in the magazine. The nose must ride on the front of the magazine in such a way as to keep the cartridge at the proper angle. There should be a little space between the case mouth and the next case mouth below it. If the cartridge is too short, it will tip and contact the next one above or below for the full case length. The optimum OAL for a truncated cone will be a bit longer than for a round nose.
Also, since the cartridge must ride on the magazine front, the edge of a large open hollow point may drag.
This was originaly so designed to allow a tapered case to function in a straight magazine. Most 22 LR magazines operate on a similar principle to allow for the rim.
the mystery, is what bright boy decided the SAAMI 9 mm round should be shorter than Georg intended it to be.
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