From the Industry Forum I read that these features available on Colt M4/MT6400C are supposed to be avaluable. Some are pretty clear, but others don't look so. Can anybody explain me more?
1] M4 feed ramps
2] Staked down castle nut on collapsing stock
4] Proper height front sight block (F-marked) to actually allow one to sight in the rifle properly with a flattop. ???
5] Magnetically tested and proof load fired Bolt and Barrel with a 77k psi 100gr load. Each and every bolt and barrel is done. Is it true?
7] Enhanced extractor spring is standard
8] H-buffer Gotcha
12] Colt has the real M16 carrier, that features a shrouded firing pin, and more metal at the rear. This looks Black Magic
From my limited knowledge.
1: Smoother feeding. The feed ramps on the M4 are longer and some barrel extensions are made with them in mind. I don't believe it's really needed on anything but a 14.5 inch barrel though.
2: Keeps it from coming loose.
4: Some manufacturers have different heights of front sight posts. Unless you use their carrying handle or replace the front sight post, you probably won't be able to get enough elevation adjustment to zero the rifle.
7: The shorter gas system of the carbines is harsher and sometimes the fired caseing isn't extracted. The stronger extracion spring makes it much more likely that the extracter sill grab the casing.
12: Not legal in every state. The metal is removed from the rear so that it can't trip a full auto trigger, and the less shrouded firing pin is IIRC supposed to catch a hammer so it can't fire full auto. Some states say that it's illegal to have any part of a machine gun in any weapon.
+1 on what they said
edit: have fun with your rifle!