Short answer, NO.
Longer answer, I'm not going to type it all out again, try reading through some of the other threads about the ACR.
To me the x39 round is for red rifles not black rifles. I don't care how cheap it is. The magazine of the AR-15 was not designed to work with a tapered case like the x39 so there will always be reliability issues.
If you decide to try 300 Blackout I can help you get a conversion built.
If you want a x39 built try Ian at Herron Arms and see if he will help you. It will cost you around $1000 though.
Any conversion that requires a different bolt head is going to be more expensive.
Keep on mind that once you declassify it and it is non restricted you can never put your 16 inch barrel back on, even if you are at the range. You will be in possession of an unregistered restricted firearm and you can be charged and jailed if you are caught. The only way to do it legally is to call the CFO and have it re-registered before you put the old barrel back on. So stealing all the gas system parts off the factory barrel is not a bad thing as it will keep you out of trouble and save you over $500 in gas system parts.
