I want to have a CMMG RDB barrel cut down to 3.5"-3.25" in length and then have a 3-lug integrally cut into the end.  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.  Can anyone recommend a gunsmith that can do this for me?  And please don't say "Tros"; yes they do good work but I want to be able to shoot the thing sometime this year. And I'm not interested in cutting threads and using an adapter.

And before asking:
yes, there's enough meat on the barrel to cut the lugs (I measured) and the nose of this 3-lug adapter is longer than normal (.824", typically) because I want my muzzle to be flush with the 3-lug adapter I'm using (which happens to have a 1.5" piston sleeve on it).

I want to turn this:

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into this:

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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