The 1911 main spring is often overlooked for it's importance in the correct operation of this pistol. I offer three spring rates to cover the different sizes and calibers commonly found in the Government Model and Commander sizes and one additional spring for the Officers ACP. The standard main spring weight in a .45 ACP Gov't Model is 23 lbs, most commonly paired up to a 16 lb. recoil spring. Competition shooters and medium caliber pistols such as the 9 x 19 or .38 Super normally find a 19 lb. main spring the right weight to give proper function. Delta Elite owners are advised to use a 25 lb main spring and a square bottom firing pin stop to help control recoil and retard slide speed.
When you shorten the slide length, you may need a tuned, square bottom firing pin stop firing pin stop and a heavier main spring to help control muzzle flip and improve reliability by retarding slide velocity. There are too many variables to cover in detail, but this should give you a starting place.
Gov't and Commander models use the same spring and should last almost forever. The shorter framed Officer's ACP size pistol (and any pistol with an Ed Brown Bobtail conversion), uses a shorter spring that's larger in diameter. These springs do not last very long as they are somewhat over-stressed in use. I change mine ever 500 to 1000 rounds, or as needed.