Maybe a stupid question

[Sam]

What is "F marked front sight base" ? What's the F? :confused:

[MASP7]

Colt grades the front sight bases, A through F.
You got a bad one...

Actually, it denotes a "Flattop" height front sight base.
They're a bit taller than the standard FSB.

[Sam]

You're freaking me out dude :D

So if I have a flat top upper, I should get the F front sight? Will it work with a Larue BUIS?

[MASP7]

You should be OK.

If you find you don't have enough adjustment (up), you would have to get the tall front sight post. This is a lot easier and cheaper than changing out the front sight base.
Shoot it and see before you do anything.

[deadwood83]

Is the Bushmaster M marked FSB the same as a F marked? I just noticed that there's an M on my FSB and an M right above the gas tube hole on my flat top receiver.

[Robb Jensen]

Is the Bushmaster M marked FSB the same as a F marked? I just noticed that there's an M on my FSB and an M right above the gas tube hole on my flat top receiver.

That should be a crown that's cast into a Bushmaster FSB. It's FSB is shorter than a Colt or other F FSB. The 'F's are stamped into the FSB.

[deadwood83]

Ok so next question; will the KNS globe sight make up for the lack in height? It sure seems to be a tall bugger.

ETA: Oh yeah it is a crown. The pin goes through the forwardmost point so it looked like a slanted M at a glance.

[Robb Jensen]

I don't know but I do know that Bushmaster makes a taller front sight post to make up the difference.