"F" FSB & Troy Flip-up

[M4arc]

I have a Sabre mid-length upper with a Troy BUIS. My front sight base is marked with an "F" but the front sight post is cranked up pretty high. I'm trying to figure out what is wrong here; is it the front sight base or is it the Troy BUIS?

Did Sabre use a standard FSB and just mark it with an F or does Troy build their BUIS to match the original height of an A2 upper?

[Paulinski]

Have you tried measuring the height of your front sight base?

GotM4 here has a picture indicating the height difference between F-marked and standard FSB.

[C4IGrant]

We have seen a lot of F marked FSB's that are too short. You might have gotten a bad one.


C4

[Robb Jensen]

Not my pics, I found them on another website.

[KevinB]

My Troy's work with Colt F marked FSB's on M4A1's (real ones), LMT's, KAC, and CMMG F marked FSB....

[DRich]

I installed a Troy BUIS on my Sabre Defence M4 a couple of weeks ago and works just fine.

[M4arc]

Thanks guys, I'll try and measure it to see what's up. I suspected that it's just a normal FSB marked with an "F" but I guess the measurement will tell me for sure.

I'll let you all know what I find out.

[AR15barrels]

Not my pics, I found them on another website.

Proper credit for those pictures goes to Molon on Arfcom.
I use those pictures as well.

[Shihan]

Proper credit for those pictures goes to Molon on Arfcom.
I use those pictures as well.

You using pictures? No way!

[mudrock]

Thanks to the pics I think I understand the difference between standard and F-marked front sights.

Why is there a difference?

Are A1 and A2 handle attachments usually made to replicate the original receiver, or to suit F-marked
front sights? Is there any practical difference?