I just ordered a LMT CQB MRP piston in 5.56. I was looking in to barrel/caliber change and noticed on the LMT website the 300 BLK is DI gas. Does this mean if I wanted to swap my piston 5.56 barrel to DI 300 BLK I would need a DI BCG also, or could I just change the barrel and use the current BCG?