As WarPig noted, the case length is not an issue (unless it is too long). In firing an auto pistol the cartridge is stripped out of the magazine, slides up the breech face and under the extractor where it is held. There is no way that you could trim and load all your ammo so that it exactly headspaced on the front of the cartridge case. General Hatcher demonstrated that firing too short brass in a pistol (auto) made no difference. He fired the .380 ACP (9mm Kurz) in the 9mm Luger. As described, the cartridge was held against the breech face and fired normally other than the fact that it didn't have enough power to cycle the action. Pull the toggles back, release them, and another cartridge was loaded ready to fire.

I don't know about 9mm Luger, but .45 ACP shrinks in length with use. Have never trimmed .45 ACP brass either. Just load your cartridge to the proper overall length.