Well in this picture it's actually held on by a black showlace (you can kind of see it near the base of the barrel here) but I've recently modified it so it's now held on with two nicely hidden bolts
I see you sneaking and all I can think of is that Roosterteeth vid where Caboose roes to the campaign mode in Reach. XD though you probably heard that one before! Kudos for the great work!