Well, I have quite a number of pistols in .45 Colt. They run from Cimarron, through Ruger, to Smith & Wesson. Some have small cylinder throats, some have large, some have small grooves, some have large.
Forget all the baloney about oversized lead bullets being a problem; it just is not true unless they are so large as to prevent ammo from chambering. You can easily swage down a lead bullet in a lubricator-sizer with hand pressure anytime you want. How then is an oversized lead bullet, hard or soft, going to be any real problem in a gun? Well, they are not, at least from a pressure standpoint.
I have an old Cimarron Model P that has oversized (O.458") cylinder throats. I shoot 0.458" bullets in this gun, but its groove diameter is 0.452". No problems whatsoever, anytime. (I had a custom bullet mould made and cusom loading dies made, too).
I have a Colt Python with an 8" barrel, a target gun. These guns are famous for having 9mm bores and the grooves run right at 0.355". I regularly shoot Remington swaged lead bullets that run 0.360"+ and never have a problem.
Just make certain that your bullets are at least as big as your cylinder throats. Then, as an added precauton, get a slightly larger inside expander plug and us it (0.454" for 0.454" bullets). The problem is that modern expanders leave the cases very tight (as needed for jacketed bullets) and the tight cases will resize a soft lead bullet when it is seated, thereby destroying all of your efforts to get a correct size on the bullets.
Don't shoot bullets any harder than absolutely necessary to keep from leading. Standard .45 Colt loads only need bullets about 1:20 Tin:Lead to accomplish this if they are correctly sized.
Use the softest, gooeyest lube that you can. Soft lubes are a tad better at low pressures and with black powder, too.
Try some black powder loads, they are really fun and the .45 Colt is at its best with them.
