The photo below was posted by a group member showing his collection of various Colt LMG type upper receivers. Comments below are his.

“Current line up of LMG uppers.

I have a barrel for another version that I snagged and just need to assemble it. Also need a 606 and that should round it out. I know they have a 941 as well which was a flat top version of the 741 with an a2 barrel.

Prototype stainless VP marked barrel
721
741
Gen 1 Diemaco LMG
Gen 2 Diemaco LMG
IAR
Prototype SBR IAR”