Maybe I misunderstood your first statement. Thought you meant the mil. wanted weapons that only mil. mags would fit and that's the reason the 19x mag well and baseplate are made that way - to keep civ. mags out, for some reason. If so, the AR/M4 didn't adhere to that standard. And yes, Magpul is now Marine approved and may even have the contract.Military is all about standards. Really magazines for M4 carbines that are not issued are not authorized. Using magpul mags was technically unauthorized even though people did it. Though I think they may be authorized now. Not sure.