"BTW, Sigs often have pretty tight chambers, so when you make the transition to cast bullets, sized diameter will become critical to function. The .452 and .453 that other .45's love will gag up a Sig immediately."

I'm not completely sure that statement is accurate. My SIG P220 digests .452" bullets without any problem at all. can't say about .453" though as I don't have a sizing die that size and my SAECO #068 mold casts bullets right at .4525". I would have to try a .454" sizing die as the next step up but that one is reserved for the .45 LC.
That SAECO mold BTW is a clone of the famous H&G #68 and it feeds like pork fat through a goose in several 1911s as well as the P220. it's my all time favorite bullet for the .45 ACP. Three of my 1911's are for all practical purposes full blown target of combat pistols. The Colt Combat Commander is my sometimes CCW piece, at least in the winter and then there's the SIG P220 which shocked me by being just as accurate as the three target guns. Two of the 1911s were built by the late F. Bob Chow in San Francisco. Bob was a good friend back when I lived in San Francisco as when I was a kid, I'd hang out in his gun shop and was a general all round pest. When I came of age he made me a 1911 combat pistol and later made med another that was an even more serious gun. The last 1911 was somebody's hybrid I picked up at a gun show, a Caspian frame with a Colt Gold Cup upper. The frame looks rough and crude on the outside but that gun will keep ten shots under two inches from a rest when I do my part. The Combat Commander is almost strictly stock as I just polished the feed ramp and throat and replaced the grip safety with a beavertail type. The tiny tang of the CC lets the hammer dig holes in the web of my hand and shooting should be fun and not draw blood. The last one is a Colt Gold Cup Combat Commander. From what I understand they made something like 500 in blue and 500 in stainless steel and they now command quite a premium price. Even more so if you have both types. I'm still looking for the stainless one.
I haven't shot the .45's lately becaause I have to sit down and cast up a couple thousand bullets and then load them in the brass that's prepped and ready to go. This time of year it's too hat to do that and if I use the A/C out in my shed while castimg, the electric bill will go way the hell out of sight. Not much fun casting when it's 110 in the shade.
Paul B.