FYI the term "barrel shroud" is a firearm term and not just a paintball term. Also, it includes more than just rail systems or handguards.
Anyways...there are different brands and styles that connect in different ways. Many connect with the delta ring (the ribbed ring at the base of the RIS in the 1st pic) while others connect with their own barrel nut that replaces the delta ring.
M4s can take almost any brand of rail system or handguard...as long as it doesn't have a barrel nut with opposite threading as the upper receiver...
Danger Close D43
Last edited by Maethori; October 25th, 2012 at 20:46..