Quoted:
I just got the Bushmaster X15  M4 Moe magpul.  Detachable rear mbus sight was in the box. But I'll be darned it does not seem to possibly fit the rail.
Has anyone had trouble trying to figure out how that front site can be attached.

Note - first post was in error I stated front site but actually I was talking about the REAR MBUS detachable site


Resolved---- Operator error on my part.       Case of the dummy set in - I was too gentle pushing it on the rail