FSB Height on BCM lightweight uppers [Archive]

IZinterrogator

01-04-12, 22:50

Are the FSBs on the BCM lightweight uppers true F-height FSBs or are they just an A2-height FSB with a taller front sight post like on the Colt 6720? I'm not sure about the specs listed on the website because they all seem to say the same thing regardless of configuration.

Kyohte

01-04-12, 23:57

Mine is f-marked.

IZinterrogator

01-05-12, 00:04

Thanks!

Froader

01-05-12, 00:10

Any flat top upper from bcm will have a f marked sight base.

spamsammich

01-05-12, 00:47

I thought this was clearly stated on their web site.

markm

01-05-12, 08:39

I don't think you can get any non F marked FSB from Bravo.... Since they don't have any fixed carry handle/A2 uppers. :(

Dionysusigma

01-05-12, 10:41

Ever BCM upper I have, lightweight and "standard," has an F-marked FSB. :)

Terminator2003

01-05-12, 13:53

This is an interesting question that has piqued my curiosity now. I have a BCM lightweight middy and it has the F marked sight. I didn't know there was a difference between heights on the fixed sights. I just assumed they were all the same standard height. Does this mean that if I put on a standard A2 type carry handle that it won't line up correctly? I ask because I plan to buy one shortly, and won't waste the money if it won't line up. Also, will standard flip up sights align correctly?

eodinert

01-05-12, 15:31

Yes, if you don't have the F height front sight base, things won't line up.

Usually how this manifests itself is when someone gets a good deal on a barrel (or buys an A2 upper for cheap) and mounts the barrel on a flat top upper. When you go to zero, the front sight is screwed way out, and the top of the sight is sticking up past the ears on the FSB.

Terminator2003

01-05-12, 16:04

Yes, if you don't have the F height front sight base, things won't line up.

Usually how this manifests itself is when someone gets a good deal on a barrel (or buys an A2 upper for cheap) and mounts the barrel on a flat top upper. When you go to zero, the front sight is screwed way out, and the top of the sight is sticking up past the ears on the FSB.

Ok, thanks. I guess I should be gtg since this is a factory built BCM upper, and has the "F" marked base. I got worried seeing this thread because as I said, I was not aware there were different heights for the fixed sights. Just to clarify the "F" marked base will line up with say a Colt removable carry handle - correct?

DeltaSierra

01-05-12, 16:05

Just to clarify the "F" marked base will line up with say a Colt removable carry handle - correct?

Any carry handle made by Colt or BCM will be fine.

Terminator2003

01-05-12, 16:15

Any carry handle made by Colt or BCM will be fine.

Awesome, thank you. the one I want is a new Colt 6920 takeoff.