Colt AR15A4 front sight base and receiver markings

**wally05** · 08-17-17, 15:48

Would I be correct to assume that the AR15a4s were all supposed to have F-marked FSBs after around 2015? And what receivers have they been using. I just got mine today from Brownells and it has a NON-marked FSB and a receiver that says "AR15A4 Lightweight LE Carbine". I'm just curious.

**lt1 sport** · 08-17-17, 17:26

Which model did you buy, the 20" AR15A4 with the fixed a2 stock, or the 16" 6720 with collapsible stock because my 6720 has a .625" diameter (for the lightweight barrel) non f marked front sight post and is rollmarked AR15A4 lightweight LE carbine. My AR15A4 20" government model bought last fall has a f marked sight and is rollmarked just AR15A4.

**wally05** · 08-17-17, 17:33

Originally Posted by lt1 sport

Which model did you buy, the 20" AR15A4 with the fixed a2 stock, or the 16" 6720 with collapsible stock because my 6720 has a .625" diameter (for the lightweight barrel) non f marked front sight post and is rollmarked AR15A4 lightweight LE carbine. My AR15A4 20" government model bought last fall has a f marked sight and is rollmarked just AR15A4.

It's the full 20" AR15A4 rifle. I noticed that earlier 20" sometimes had the 6720 lower receiver, but supposedly all of that has been fixed. It's a 5 digit serial, but I need to look up the barrel date and see.

EDIT: I pulled the handguards off and the barrel is dated June 2017... apparently Colt is back to using non f-marked FSBs probably to keep up with demand.

**Mrgunsngear** · 08-17-17, 19:17

Originally Posted by wally05

Would I be correct to assume that the AR15a4s were all supposed to have F-marked FSBs after around 2015? And what receivers have they been using. I just got mine today from Brownells and it has a NON-marked FSB and a receiver that says "AR15A4 Lightweight LE Carbine". I'm just curious.

I just got another from Brownells and it has a non C marked carrier as well. I realize this has been discussed at length but just adding another data point.

**wally05** · 08-17-17, 20:14

Originally Posted by Mrgunsngear

I just got another from Brownells and it has a non C marked carrier as well. I realize this has been discussed at length but just adding another data point.

Yeah, I just noticed that while doing the deep clean. I didn't know if there was a discussion on the recent ar15a4s that had come out. I had not found many recent threads on it. I just found a member on another board that got a rifle exactly like mine three weeks ago from another retailer. Colt stated that the receiver and fsb were confirmed mistakes and took his rifle to give a replacement within two months.

The wait time isn't worth it to me. I can always replace the fsb and my paperwork matches the receiver serial, so I'll have prove it isn't a pieced together rifle.

**Iraqgunz** · 08-17-17, 20:16

Good luck with the FSB replacement.

Originally Posted by wally05

Yeah, I just noticed that while doing the deep clean. I didn't know if there was a discussion on the recent ar15a4s that had come out. I had not found many recent threads on it. I just found a member on another board that got a rifle exactly like mine three weeks ago from another retailer. Colt stated that the receiver and fsb were confirmed mistakes and took his rifle to give a replacement within two months.

The wait time isn't worth it to me. I can always replace the fsb and my paperwork matches the receiver serial, so I'll have prove it isn't a pieced together rifle.

**wally05** · 08-18-17, 00:12

Originally Posted by Iraqgunz

Good luck with the FSB replacement.

Haha. Is it as bad as removing a BCM one? I've done both (off a 6920 and a BCM LW barrel) before during an armorer course and in my free time.

Like I said, it's not a big deal to me. I was just curious if others with recently built rifles are seeing the same. I'll play with the idea of calling colt.

**Iraqgunz** · 08-18-17, 01:06

Removal isn't hard with the right tools. It's trying to install one on a barrel where an FSB was already in place.

Originally Posted by wally05

Haha. Is it as bad as removing a BCM one? I've done both (off a 6920 and a BCM LW barrel) before during an armorer course and in my free time.

Like I said, it's not a big deal to me. I was just curious if others with recently built rifles are seeing the same. I'll play with the idea of calling colt.