Here's my dilemma I have bushmaster AR and love it. Now I want to get a .300blk upper for it. From my understanding I can use the same mags and same bolt and BCG for the .300blk. But some people seem very adamant that you should get a new BCG for each upper so the two wear evenly together. My question is how big of a deal is it really and are there any safety issues or is it only a wear issue if I shoot tens of thousands of rounds. My plan is basically to only use the .300 during hunting season.