I have necked it down as far as 17 caliber. Dave Kiff, at Pacific Tool and Gauge made the chamber reamer. The only 2 calibers I played with on that case other than 45, was 357, and 17. RCBS has made dies for someone else that did a 17 on it. It can be a pain in the butt to neck down when you pass around the 30 caliber mark. It took 11 dies to go from 45 to 17 caliber. You can get there with fewer dies but the less dies you use the more cases you lose. It is a very strong case, but there are other cases that will do just as well with a lot less work. When I was a kid and first got interested in wildcats I was asking an old man that built wildcats"Why people built them". He told me that if you have to ask you will never understand. The older I get the better I understand what he was saying. Over the years I have built from a .10 caliber to a 12 gauge slug gun. I'll be the first to admit that some were not worth the time and money spent on them. The thing about wildcats is you can't build just one, and logic is not always a factor in the creation of some of the best. Build one if you really want to find out what it will do. You will at worst case have a "One of a kind", and that ain't bad.