From the vault: A reader-submitted question about .45 ACP cartridge overall length. As published in the October 2001 issue of Shooting Sports USA.
Q. I am confused in reloading .45 ACP. I read 0.898-inch is the maximum case length. I have never measured one that long. Some manuals say trim to 0.895, and some say trim to 0.893, but most of my once-fired cases are shorter than 0.890, though I have a large supply of 0.890-inch cases. What is confusing to me is that cases don't shrink when fired, and some cases are 0.890 after firing. Can I trim them all shorter than 0.893 to 0.890 without a problem?
A. We've never seen a .45 ACP case that needed trimming. The maximum case length according to industry standards is 0.898-inch with a tolerance of -0.010-inch. That means cases measuring 0.888 are still within standards. Some are even shorter with no ill effect. The minimum chamber length is also 0.898 with a positive tolerance of 0.004. This means there would hardly ever be a situation where the cartridge case would be long enough to touch the chamber shoulder, much less be too long. As long as your cases do not exceed 0.898, there is no cause for concern. Some say that a uniform case length is necessary for good accuracy, but my tests have shown that case length is not a factor.