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Hmmm, that almost sounds like what you would do with a revolver cartridge roll crimp, not the typical taper crimp on a semi-auto round. None of my semi-auto bullets have a cannelure as I recall, and I apply only a mild taper crimp with my Lee FCD. I've never seen any problems with the bullets moving around in the case. I confess that I've never measured the case diameter of the finished product, but have dropped a few into the barrel to make sure they sit at the correct depth. I was under the impression that most/all .45 ACP cartridges head space on the case mouth, not on the extractor.
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Here was there exact reply:
"I can see from the pictures that you sent there is a pronounced edge at the case mouth. Increasing the crimp will not increase the pressure to a dangerous level unless you are right on the edge of maximum already. The pressure required to push the bullet out of a crimp is measured in hundreds of pound per square inch (psi), the peak pressure developed in a 45 ACP is somewhere north of 10,000 psi.
Despite what you read, many semi-automatics actually headspace on the extractor. The extractor is the hook that pulls the empty cartridge case out of the barrel after the cartridge is fired. This hook is usually stout enough to keep the cartridge pinned against the breech block. Try loading a few cartridges with the case mouth crimped into the top lube groove; This will make for a more gradual ramped edge for the case rim of the case being extracted to ride up and over the top cartridge in the magazine.
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I also find it really strange that the magazine holds the following round high enough to contact the case being extracted. Could the feed lips be bent and holding the front of the top round too high? The extractor sure puts an ugly rip in the brass, I've only seen that happen with .380 ACP, most of which seems to get torn up a lot.
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Another user here had also suggested modifying the magazine feed lips to try and tuck the bullet down somewhat. I only want to do this as a last resort since the firearm cycles factory ammunition with no problems. This is clearly an
ammunition problem and not a firearm problem.
Basically, the bullets in the magazine are held down by the slide, until the slide is blown back and the opening in the slide passes over the magazine - then the top bullet snaps upward until it bears against the feed lips. Of course, the spent case is being pulled back at the same time. I guess what is happening here is that as the slide comes back and the nose of the bullet in the magazine is no longer trapped by the slide, it is popping up against the feed lips fast enough for the extracted case round to hit it.
Maybe if I didn't seat the bullet so deeply the longer bullet nose would keep the cartridge "pushed down" a bit longer.
The extractor is tearing the rim because the extracted case is jamming against the incoming cartridge and the case rim isn't strong enough to stop the slide and extractor from going back.
Steve