I have a Sig 516 pistol that I want to convert to 300BLK. I called Sig to for info and was told that the gas block and barrel are one unit and they would both have to be replaced. This would mean I'd also have to replace the BCG as it's a piston system. Can anyone confirm that a simple barrel swap is out of the question. The only answer I can come up with is getting a second complete upper in 300BLK. Once I make the switch, I don't plan on using the 5.56 upper anymore, so I'd like to use as much of it as possible. what are my options?

Thanks in advance for the help.

I think I'd buy the complete upper and sell the 5.56 upper to make some of your money back, it can be used on any standards mil spec lower to make a complete riffle, as far as your original question you may get more in depth feedback from the Sigforum being its a Sig.