Nope not a real M4 barrel, those are made by Colt and are 14.5" in lengthhttp://www.rockriverarms.com/item-d...age=bblr407.gif&CFID=6373035&CFTOKEN=27100757
I figured it was an RRA-only term, so this is the "real" M4 barrel? Is there any worry with a mid-length rail because of the indentation towards the muzzle?
If you look at the pictures, the lightweight barrel is obviously not flat along the outside (some areas are higher than others). Is this anything to worry about as far as uppers or rails? What is the purpose of these changes in diameter?
With a 16" M4 barrel, can you not use a mid-length handguard, such as a quad-rail free float?