PJ, I still feel if you keep to the IMR load data you will get the velocities you need. Maybe you noticed this one but I will mention it anyway, if you scroll down to the bottom of the load data page there is usually a added load for not so much used bullets such as lead cast swc and other bullets for 45 colt. Just click on the + symbol. Also a note on things that change muzzle velocity. About barrel length, I just had had my Uberti 1873 45 Colt converted to 45 ACP so I can use the same ammo and load in my lever action as I do in my 1911 for Wild Bunch matches. Now that said, THIS defies all reason! I ran 20 rounds through both the 1911 and the rifle and my chronograph clocked them at 896 fps for the 1911 and 902 fps for the 1873. Now others that have done this conversion before me have said they had this same result but I just could not get my head around the fact that firing the same round through a pistol with a 5 inch barrel would not increase by a couple of hundred fps when shot through a rifle with a 24 inch barrel. Go figure. They were right on the money. Anyway, good luck with your venture, and happy & safe shooting. W. L.