[who101]

I am going to kill to birds with one stone here
(or if your Chuck Norris, kill two stones with one bird)

Question #1
How do you know if a part fits or not, like if you want to put a new RIS hanguard on an M4, how do you know if it fits
are all part universle (some brands better then others)
or will the same brand of parts only work on that brand

Qestion #2
in a ealiar thread I lerand that you need to by sepperate, threaded, barrell if you wanted to add a silancer
I wanted to get a KJW colt M1911 MEU, but I could not find a barrel anyware
what I am asking is that either anyone out there knows were I can find one (no, the clissifids don't count) or if a metal pistol barral can make over the border, so I can "xpand"my serch