Build a inexpensive blaster truck gun.... why not ?
Do easy tuning tricks on the upper ... lap the receiver face true, shim / Loctite the barrel in.
Install a Aero .750 Adj. Gb on the barrel.
I have quite a few GTG DC Machine / PSA SS 308 barrels that have been shooters. ( I wish they would bring back the Nitrated 308 barrels )