Unlike high pressure cartridges with a significant taper or bottle neck which are stretched to a greater length when fired, the 45 Auto case is essentially a straight case and doesn't change length significantly when fired. Because of that I don't think there are many reloaders of the 45 Auto that trim or even measure their cases. I've been reloading it since the mid-1960s and don't even own a case trimmer. Never bothered to measure case length either, except on rare occasions. The average of those I have measured and recorded works out to 0.894 ± 0.004 inch. There are even some who claim 45 Auto cases gradually shorten due to repetitive resizing.
My RCBS taper crimp seat/crimp die has a taper such that for every 0.001" change in case length, the case mouth OD changes by 0.00027". Because of that, I don't concern myself with case length.
You are correct in thinking trimming is unnecessary - unless you're a member of the 1911 Bench Rest Shooter's Association.
Regards
When you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind. [Lord Kelvin]
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