I have a 20" flattop BCM upper with M4 feed ramps, but I've decided to convert it to an A2 rifle. Most of the A2 fixed handle receivers are standard feed ramps, anyone know of any manufacturer that has an A2 receiver with M4 ramps?
I've never heard of an A2 upper that had M4 cuts. No doubt someone has used a Dremel to convert one. The A2 upper with the barrel with M4 cuts shouldn't be an issue unless you're going to use rounds that are fussy feeders for some reason.
I've built several rifles for myself and friends/family lately. When walking them through a build sheet, I've been careful to explain the M4/A2 cut and compatible combination. After all that explaining, every barrel I've seen lately has had M4 cuts, as has every upper receiver.
I believe manufacturers have standardized the M4 cut on everything.
It was my understanding that the M4 cuts came about because the bolt cycled so fast when the 14.5" rifle was shot in full auto. The cuts made it smoother to load with fewer jams when the bolt was going so fast. Prior to that there were no M4 cuts on anything including the M16. I'm not sure you can shoot fast enough to be concerned with the cuts unless you get a full auto short barreled rifle.