What is the shortest legal barrel length on a post-ban Bushy XM15-E2S?  Does this length include the flash suppressor?  I want to have different uppers for my Bushy, but want to remain within the laws of the BATF.

Minimum barrel length has been 16" for decades, got nothing do do with the 1994 Crime Bill.

Can't use the length of a flash suppressor as they're illegal per the Crime Bill.  Can use the length of a permanently fitted muzzle brake, however.

Official barrel length is measured with a rod down the bore to the face of a closed bolt with the weapon cocked (firing pin retracted).

Bushmaster 14.5" M4 barrel + permanent brake qualifies as do regular 16" bbls.

As a historical foot note the 18" barrel length for shotguns and rifles used to be the same.  Government release of the M1 Carbine to surplus sales required a change in the law as those barrels are 16".  Shotguns remain 18".

-- Chuck