FSB Question

[Diesel]

I was trying to determine what FSB came installed on my rifle. It's not stamped, so I assumed it is a standard "rifle" FSB. I measured it as they did in this image below and mine came out about 1.865".

Does this seem normal? It's on an Oly with a removable rear sight/hand rail. Since I will be installing Optics soon, I want to install a Magpul BUIS and wanted to make sure that the FSB would be compatible.

http://img.photobucket.com/albums/v408/gotm4/FshelfColt.jpg

Credit to GotM4 over at M4Carbine.com for the image.

[wareagle700]

That seems a little short. I had a similar rifle from Oly a while back (Flat top M4 profile). It worked fine with a flip up rear sight.
One thing you might have to do is buy a taller front sight post. DPMS and Midwest Ind. make these. They are .03" taller than a standard front sight post and are designed to give you a proper front sight height while fully engaging the detent and spring.
Good luck!

[Dos Cylindros]

My first build had a standard front sight base (non F marked) and usually they don't have the right amount of adjustment to work with the most common types of BUIS. You just need to buy the taller front sight post. Bushmaster makes them, and that is where I got mine. They are actually .04" taller and are an easy install as long as you have a front sight tool. Go ahead an order one up, they are very cheap. It has me wondering why yours is so short, hopefully it is just a measurement issue on your part (no offense), because if it is that short, you migh thave issues even with a taller front post.

[Diesel]

I'm measuring it with digital calipers and unfortunately, I have to do it while it's still mounted on the barrel, so I could be off a little, but it's not even close. I was planning to pick up another from BCM on my next order and go a head an replace it, but I wasn't sure if it mattered or not.

[Eric]

For the most part, FSB are not user changeable. They are drilled after installation and matched to the specific barrel they are on. Clamp-on versions are available, but lack the strength of the original pinned on ones. I've seen several OA guns come through classes and many have the front sight post spun out as far as they can go in order to get them dialed it, while others have been fine. Try getting it zeroed as is first.

[Diesel]

OK, didn't' think of that. I was thinking that another manufacture'rs would fit...I guess the odds are that it won't...thanks for pointing that out for me.

I just got the rifle off my dad a couple weeks ago and I don't have anywhere locally to shoot as of yet (pending local gun club membership), but I have shot it before, but he had a scope on it...knowing him, it should already be zero'd.

[Diesel]

I remeasured it again today, the measurement in my OP is correct. I wonder if the hand guard / rear sight is a little lower profile than most?