There's a famous chart showing all the brands of M4 clone compared to each other attempting to show how close to mil-spec the vendors are getting.
Just for fun, I figured out what the Colt AR-15 model R601 had in comparison to the chart. Bold where it has the desirable feature.
No MPI bolt, No HPT bolt, No shot peening, No extractor spring insert, Improperly staked gas key, M16 bolt carrier, 4150 barrel steel, No MPI barrel, No HPT barrel, No chrome in the barrel, but the BCG is, 1:14 rifling, 5.56 chamber, No M4 feed ramps, Rifle FSB, Taper Pin FSB, Parked under FSB, single heat shield, 1.12 receiver extension, No castle nut at all, rifle buffer, 0.154" FCG pins. Fixed rear sights, what warranty, $32,000+ if you can find one.
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