Hi. A lurker emerges. Thanks, all, for all the great info so far.

I have a pre-ban Sporter Lightweight (R6530) with an A2 receiver. I would like to make it a flat top but I am not sure what A3 receivers will mate with my 16" Lightweight Sporter barrel.

Colt customer service says I cannot use an M4 flat top receiver, they won't mate. Anyone know any better?

Any other ideas for receivers that will mate? I would prefer to stay all Colt but would be open to another high quality receiver.

TIA,

Subliminal

Colt is full of it. You can use any upper you want, but if you get the Colt M4 upper, you have to have the barrel cut with the feed ramps to match the upper, or it will jam. If you buy a Bushmaster upper, you can send them your current upper and they will swap and headspace for you, and send the A2 back with it.

I suggest you buy a Colt upper, and have the M4 feedramp cuts made into the barrel to match the upper. That way your gun remains collectable, or even increases in value.