This topic was touched upon in an earlier post. By chance I pulled out an old "Shooting Sports USAicon" magazine from Sept 1991 (good periodicals, glad I kept mine.) It had published test results by Hugh Birnbaum on measuring 45 ACP case lengths. Min spec case length is theoretically 0.888, and max is 0.898. He resized and measured hundreds of 3x fired Federal and once fired Sampson (IMI) cases. There were great variations in case lengths, and significant number of the Federal were well below 0.888.

I measured a box of 50 Federal 7x resized, and a box of 50 IMI Match 2x resized. The Federal averaged about 0.888 with about 2/3 from 0.883 to 0.887, w/longest at 0.892. The IMI averaged 0.890 with all above 0.888, and much better uniformity, but still with significant variation from 0.888 up to 0.895.

I then did some searches on the internet on this topic. Consensus from the internet and the referenced article seems to be that .45 ACP headspaces on the case mouth only in THEORY, and in reality cases probably are held in place by the extractor. Of the 3 instances I found where someone had measured their 1911 chambers, all were about 0.900.

Bottom line, nobody seemed to care too much about .45 ACP case length, nobody bothers to ever trim cases, and nobody worried bout having cases under the 0.888 length. I have yet to find any of my cases over 0.898, but will continue to check periodically. As mentioned in an earlier thread, .45 ACP cases seem to shrink with continued reloads. I once knew a skeet shooter who used very old 12ga brass cases, continually reloaded them never discarding any. Guess the .45 ACP cases are somewhat like that.

I did have some PMC cases in a recent lot where some primers would not seat fully, first ever that has happened. In my "research", some folks did express concerns about high primers in reloads, but I could not find any instances of "slam fire" documented. However, I share concern about high primers and will not tolerate that in reloads.
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