If I get around to making the 357-5.45x39 round I most likely will make an undersized chamber reamer and make a sizing die, or try to modify a 5.45 die set. Either way it's a lot more work than using off the shelf die sets. Here's a pic of the five 357 reamer attemps including the screw ups. The top reamer is a 3-flute that I tempered too much and ended up too soft. The 2nd down is the reamer I chambered my test barrel with which was a 357 1-20" twist with a .346" bore and .356" groove diameter. The 3rd reamer down I feed in the wrong amount and knew it right away so I just used it as practice. The 4th reamer blank down I snagged the cross feed knob on my jacket pocket which caused it to feed in slightly and leave a mark on the begining of the rifling leade. The bottem reamer is the one I used to chamber the finished rifle in the pic which has a 1-14" twist, .350" bore and .358" groove diameter. A 1-20" barrel is supposed to stablize up to 160gr, and some 180s but not all. I wanted to shoot mainly 160-200gr so I went with the 1-14" twist. The headspace gauges were also easy to make for a straightwall case. I only made a go and no-go gauge since I'm chambering a new barrel. If the bolt ever closes on the no-go I'll make a field gauge. The bullets next to the gauges are top sierra 200gr rn, middle hornady 180gr psp, bottem hornady 158gr sjhp.