Quoted:
I could probably attempt this myself and I made a basic print that can produce what I'm looking for using just a lathe and a mill (with indexing rotary chuck)... but I've never made a 3-lug anything and I'm not sure I want to risk learning on an expensive barrel made of nitride hardened 4140 steel.
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Simple answer is don't learn on the expensive barrel.
I've ordered "less than perfect" barrel blanks from Green Mountain (whatever was on sale as i didn't care about bore size or twist rate) to use as practice pieces when learning new skills. For under $100 I got
a lot of blank stock. So much that I have a lifetime supply thread protector raw material left over.
Yes it means making the thing twice but I go into the final project with confidence that I can do it.
Joat