USe a Ballistic Advantage bbl, 8.3" using pistol gas tube. SiCo Omega 300. If you want to build it with options and lock it all down and just go shoot, get an adjustable GB that way its done. You should not have an issue with the above, I run standard gas block.
All other upper components I had, so built it with ability to bury the can into handguard. Link below for BA complete uppers for 300 Blk.
https://www.ballisticadvantage.com/uppers/300-blk-uppers