The .460 Rowland kit has two issues that prevent a 1911 from functioning CORRECTLY with .45 ACP when it is set up for 460.
- The 460 develops much more pressure than a 45 cartridge and because of this you need a larger recoil spring to absorb the extra pressure. If you have a spring that is light enough to cycle 45 then it is not heavy enough to be the CORRECT spring for your 460 and you run the risk of damaging your frame/barrel if you do shoot 460 in your 45 setup. Vice versa, if you have your gun set up PROPERLY for 460 then the spring pressure should be too much to cycle 45 ammunition reliably.
The 460 barrel chamber is 1/16″ longer than a 45 chamber. This means that if you shoot a 45 cartridge in your 460 barrel the bullet will have to jump 1/16″ before hitting the rifling and this causes accuracy issues for the gun. Can you spring your 460 kit for 45 ammo and make it function 45 ammunition? Yes you can, but it will not be very accurate due to the bullet jump.
Our recommendation is to shoot 460 ammo in our 460 kit and when you want to go back to 45 then swap back to the original parts. Other companies may not give you this information because they want to try and sell you on the idea of being able to interchange the two, but that is only a half truth and we would rather our customers be fully informed.