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

Thanks.

Paolo