What is the best setup? A folding front BUIS on a railed free float handguard or on a railed gas block? I like the idea of the BUIS on the barrel instead of the handguard, because hard tweaking of the handguard will change POI.
Opinions?
If you want the full benefit of using a free floated forearm while using irons, put the irons on the barrel. A front sight mounted to the float tube will move with sling pressure and move your POI.
Not sure how your rig is set up but from what I understand, youre not using an extended rail. That case, I would go with a standard FSB over a flip up on a railed GB. Just get an optic with a lower 1/3 co-witness and you’ll pretty much forget it’s even there until you need it. Plus, to date there is no stronger, more stable gas block than the FSB.
Well whadoyaknow? My current setup is a 16" mid-length barrel with FSB, Omega 9", Troy Rear BUIS, and EOTech 516 which provides for lower 1/3 co-witness.
Eventually, I’ll be putting together a new upper with an 18" or 20" rifle length gas system, handguard with top rail, TROY F&R BUIS, and magnified optics which will be my coyote/predator rifle. For the time being, I’m removing the EOTech and going with magnified optics on my current setup, and anticipating the FSB will not be a problem.
I just figured I’d try to make a decision now on whether to get a 12" or 13" handguard so that I can jump on an upper if a big sale comes along.
It’s all a compromise. If your iron sights are truly for backup purposes only, you may be willing to give up the greater stability of a barrel mounted front sight. That’s what I did on my latest build, which is a 16" mid-length “recce” with a Larue 13.2 inch handguard. I wanted the extra handguard length beyond the gas block, and since I’ll be using optics nearly 100% of the time, I really didn’t want a fixed front sight visible in the optics. So I went with a folding front sight mounted on the rail. It is true that when using the iron sights the full floating rail becomes a detriment to accuracy. At least with a conventional FSB and non-free-float handguard the sling or other pressure on the handguard tends to move the muzzle and the front sight in the same direction. I would add that some rail systems are inherently more stable than others. I chose the Larue rail even though it isn’t the lightest because of its strength and resistance to rotation. (Now just imagine opening up a brand new $300 rail and using a Dremel to carve out a big hole for a Noveske switchblock. Yes, I really did that…)
I’m not a fan of railed gas blocks because (a) they limit handguard length same as a regular FSB would, (b) most aren’t pinned, and (c) most are not the same height as the upper receiver rail, and need taller front sights. Sights for these seem to be fewer and more expensive.