I love these,"which came first, the chicken or the egg", ".45 vs. 9mm lethality" , and now the M16 bolt carrier.
I am no expert since my gun business began in around 1938 with a 20 Ga. single shot when I was about 6 years old. Dove hunting, shooting them out of trees.
I have a Bushie M4 and its got the semi bolt carrier, if I had or wanted an M16 carrier I would use it but the semi one works just fine.
The "effing" BATFE changes like the autumn sky, once every day and seven times at night, you never know what they can devise to screw somebody. I will stick with my factory Bushie parts. Of course when Obama's Civilian troopers come, I may as Pappy Yoakum said, "Bounce a rifle ball off their punkin' heads" !!