Originally Posted by ryanjboutin
I have a question.
My gas block has a picatinny on it, and is lower than the receiver.
I plant on using the Magpul MBUS sights. I know I shouldn't put the polymer sign on the gas block due to heat issues.
If I put a small riser on the gas block to level out the sights, is it then ok to put the MBUS sight on that riser, or should I get a small rail and mount it on my hand guard?
Don't use the MBUS on the gas block, the heat issues could distort the front sight, not a good option.
As for the small riser rail, that won't work either because the difference in height from the railed gas block to the receiver is not the same the small risers you will find, so your front sight will either sit way to low and you front sight post will sit up outside of the ears or it will sit way too high and your front sight won't have enough negative elevation to get properly sighted in. Both are an issue. The riser will not put the front and rear sighs on the same plain, thus they will never zero correctly.
As for the "adding a rail to the hand guards" this won't work either because your handgaurds are plastic clamp ons and will move, wiggle when you hold the rifle, so your rifle will never maintain zero, even shot to shot you handgaurds will move thus moving your front sight, so that isn't even an option.
Your options are:
*replace the gas block with a different height gas block and rail (~$80 in parts)
*replace your gas block with a A2 style gas block with built in front sight at the correct height (~$50 in parts and then gun smith fees to install the cross pins properly for an A2 sight base)
*buy a front sight from MI or the like that is made from AL and it also the correct height to be used with your railed gas block (~$60 in parts) - this is the best low cost option, you also won't need armor tools and you won't have to modify the weapon, you could also likely sell the front MBUS for $30 and make 1/2 what you need for the MI sight
*buy a low profile gas block and put a quad rail free float hand guard on your rifle and then mount your MBUS to that (~$300 in parts)
*finally just buy an optic and forget about the back up sights, if you buy a quality optic it is more likely that you will be dead or dying before it stops working, so the concern with a back up set of irons is almost silly unless you are a serious bad ass