Quote Originally Posted by JoshNC View Post
It’s the bipod mounting stud. That’s a Colt HBAR m16, the model 606A.
That is the one. That's weird the barrel didn't seem to be stamped with anything...made me suspect cobbled together.

Apparently the museum doesn't know what it is and/or didn't plan on anyone looking at the info plaque and figuring the 2 don't match.