I've got a parts drawer H-bar upper I'm putting together and was entertianing the idea of jamming an M5 on there. Been a decade or more since I've laid hands on one though, so I don't really remember how they interface with the barrel behind the FSB or what max barrel diameter they will accomodate.
Can anyone confirm if this is possible without major mods involved? I do have a mil and lathe, but would rather not have to resort to butchery to make this happen. If it's going to be a major project I'll probably not bother.