<B>1 FSB?

**ROUTEMICHIGAN** · 12-23-11, 01:18

My apologies if this has been discussed before-- but the search function didn't yield any answers. I've only known F marked FSBs-- so what is this <B>1 marked FSB-- what does it mean? I saw it stamped on the right side of the FSB. My buddy said it was the same height of the F marked and he thought it just denoted the forging marks of the manufacturer? Thanks.

**Iraqgunz** · 12-23-11, 10:51

It's the manufacturers markings. I have seen them on Model 1 sales and Armalite AR's (IIRC). I think there are some LMT uppers as well.

Originally Posted by ROUTEMICHIGAN

My apologies if this has been discussed before-- but the search function didn't yield any answers. I've only known F marked FSBs-- so what is this <B>1 marked FSB-- what does it mean? I saw it stamped on the right side of the FSB. My buddy said it was the same height of the F marked and he thought it just denoted the forging marks of the manufacturer? Thanks.

**gau5guy** · 12-23-11, 12:03

The same marking is on my Colt 6450 9mm Carbine 's FSB (with a carry handle and non-LE marking). No 'F'. From what I understand, this FSB has the older and shorter A1 post, not compatible with more modern BUIS without elevation built-in (flat tops). Otherwise, I could not find any differences between the B vs F. I did alot of searching too, so thanks to you OP for your post and to G&R for your pm.

**Tweak** · 12-23-11, 12:24

completely different mark

**samuse** · 12-23-11, 12:51

I have one with the <B> on one side and F on the other.

Came on a LE6920.

**ROUTEMICHIGAN** · 12-23-11, 13:08

Thanks gents for the replies. Below is a pic of the marking. My understanding now is that it is the same height as an 'F' marked FSB and it's a manufacturer's mark (the company that actually forged it?). Apparently, some FSBs that are 'F' are not marked with an F? I put it up to my 'F' marked post and they look identical.

Attachment 10573

**Tweak** · 12-24-11, 16:58

**Don Robison** · 12-24-11, 18:33

Originally Posted by Iraqgunz

I think there are some LMT uppers as well.

Yep, I just finished an LMT upper today with that marking on it. It had been sitting in the safe since 2008 so I'm not sure if they are currently using them.

**Artiz** · 12-24-11, 18:39

Originally Posted by Don Robison

Yep, I just finished an LMT upper today with that marking on it. It had been sitting in the safe since 2008 so I'm not sure if they are currently using them.

I have an LMT upper that cleared QC Feb 25th 2010 and the FSB has this marking.