noob question
 

Does the upper need the M4 style cuts or are they a waste on the 30 cal projectile?

I have both and have never had problems with either.

Cant hurt, might help.

Mine has an M4-type barrel extension, but a standard-type upper. No problems so far, a couple of thousand rounds.

You could always use a Dremel or a chain saw file and carefully notch the reciever to match the barrel. Probably won't make any difference, it's such a small amount of material.