[Bkelly47]

The instructions say to use the spacer but I've seen ok here and other forums conflicting posts about surefire saying to not use it on SCAR barrels. I just installed one on my 16 and used the spacer and shims to time it correctly did the install with a geissele alignment rod so it's not canted at all should I be ok?

 

[Talhoffer]

The SCAR16 shoulder on the barrel is OK, it's on the SCAR17 barrel profile that usually is the problem. On the SCAR16 you should be fine.