When loading such straight sided rounds such as the 45 ACP how important is a case trimmer?

Assuming the cases are the correct length at the first firing, how often do they require trimming?

I used to shoot IPSC at about 50,000 rounds of 45 ACP a year. I bought a .452 pilot for my RCBS case trimmer but I never used it.

I have a 1911 that came home with me when I returned from SE Asia. It was pretty well used when I got it and has been shot a lot since. I've been loading ammo for it for at least 20 yrs. I have yet to trim a case. I load 230 gr round nose "hardball" or lead, and taper crimp. I'd guess some of the more refined 1911's could be sensitive to case length.

I have yet to trim any of my straight wall cases. The only round I use my trimmer for is my 300 ultra mag. I put calipers on my other bottle necks but I feel they are all within specs.

I have never trimmed a straight-walled pistol case either. Case mouth cracks seem to happen before the case gets too long.

Most likely in 45 ACP you will find that the case actually shrinks just slightly in length with frequent reloading.

officialy its very important since the case headspaces on the mouth. unofficialy since pistol pressures are so low and there is negligable brass flow - not at all

I've never trimmed a 45acp case, usually lose them before they crack or lengthen. I have & do trim .357mag, 41 & 44mag & 45colts when shooting the higher pressure loads.

I have never trimmed 45acp brass & have never needed to. It usually splits at the case mouth before it needed it.