11.5 upper

**cliffw** · 12-28-11, 17:14

I want to add an 11.5 upper to my collection of AR’s one like Chris Costa shots and every time I go to Bravo Co. they are on back order. I have built several AR’s over the years, but I’m not sure what gas block to use for this one that will fit under the Knight Armament Company URX II. What barrel would you suggest?
Thanks for any and all help.

**Hmac** · 12-28-11, 17:29

Centurion Arms makes good barrels, and they make an 11.5 CHF barrel with the thicker chrome lining that is reputedly very good. I don't know about the URX rails, but I believe a low profile gas block like the VLTOR will fit it. I would consider calling Centurion and ask if their gas block will fit under a URX.

**Iraqgunz** · 12-28-11, 17:37

Have you considered purchasing the upper and the rail separate, then cutting and grinding down the FSB? Then send them off to whomever has a URX wrench and have it installed.

**cliffw** · 12-28-11, 18:32

Hmac, Thanks for the good info.
Iraqqunz, I have a stripped upper and I was thinking if I was going to buy new parts to finish it. If I had and spare FSB lying around I would do that.

**Wicked** · 12-28-11, 19:39

Originally Posted by Iraqgunz

Have you considered purchasing the upper and the rail separate, then cutting and grinding down the FSB?

When I need a low-pro gas block, I order a barrel with a FSB and mill off the sight tower. Call me crazy, but I trust a pinned base. I KNOW it isn't moving. It helps that I've got the right machining equipment but it could be done (and still look nice) using simple hand tools if one works carefully.

**Iraqgunz** · 12-28-11, 20:35

I do the same thing whenever possible as I don't care for screwed on gas blocks.

Originally Posted by Wicked

When I need a low-pro gas block, I order a barrel with a FSB and mill off the sight tower. Call me crazy, but I trust a pinned base. I KNOW it isn't moving. It helps that I've got the right machining equipment but it could be done (and still look nice) using simple hand tools if one works carefully.

**timebandit** · 12-28-11, 20:49

Aim Surplus has a killer deal on the Spikes/KAC URXII 11.5" upper

**TACAV** · 12-29-11, 09:08

Originally Posted by Iraqgunz

Have you considered purchasing the upper and the rail separate, then cutting and grinding down the FSB? Then send them off to whomever has a URX wrench and have it installed.

To the OP,
Robb Jensen on this forum does great FSB shave jobs and I'm 90% he also has a URX wrench. You might want to send him a PM or call him up at Virginia Arms.