11.5 CQB build

AR/M4 AR General Discussion
1

Gentlemen,

I need advice for an SBR. I have a registered SBR lower that I want to make into a modern version of a MACVSOG carbine. I am looking at a colt HBAR barrel assembly with F marked Front site base no Delta ring. About $300. I want to use an A1 upper. I have used F marked Front bases before with a 20 inch upper and was able to achieve a zero. Will the carbine length sight distance prevent a zero requiring a taller sight post? My second question is I had no intention on free floating this rifle as I am building for CQB use. I was planning on a traditional look with traditional hand guard with double heat shield. But the lack of a delta ring on all of these barrels I am seeing may force my hand into a different hand guard. What do you guys recommend?

2 Likes
2

Very Cool Idea, I will follow your progress

3

Looks like Centurion Arms will make that barrel length and you can add FSB and delta ring.

4

The 0.040" taller sight post was sometimes needed to zero a carbine length sight radius to avoid unscrewing the post out past the hole/beyond the control of the sight post detent.

The F marked base is 0.040" taller to ensure zero with a carbine length sight radius.

An F marked front sight base on a rifle length shouldn’t be an issue since you are screwing the front sight further in to zero.

5

Stop me if I’m wrong but, can’t a delta ring be installed? It would require that the front sight base be removed. I would only trust a competent GS for that, I’ve used ADCO in the past with good results.

I have a Colt 723ish clone. It has a Colt SOCOM profile barrel which can’t be seen under the handguard. The only giveaway is the weight.

6

It isn’t terribly difficult to remove the FSB, add the delta ring components, and reinstall the original FSB. Replacement of the original FSB with a new one is trickier to get right. As long as you are using the same FSB it is actually pretty easy.

3 Likes
7

This is my first reaction to my build. Remove the FSB, delta ring installation, reinstall FSB with same pins.

2 Likes
8

So good, I was right ! Not used to that…. Yes, for things like this I use ADCO. In my notes I always emphasize that I will zero it first with iron sights so I need precise alignment. I think they would do that anyway but it helps me to know that they know I will be testing it.

9

HBAR? Those guns were much thinner/ lighter than HBAR, is there a reason you want to go that route?

10

I remember reading how well the heavier profile barrels performed under Molon’s testing.

But yes, I see your point. The heavier profile barrel defeats the purpose of a lightweight carbine that was easy to carry in Southeast Asia.

11

Gentlemen,

Tell me about Rosco barrels.

Rosco Husky 11.5" Barrel with FSB

556 chamber, 1:7 twist, 4150 CMV steel, chrome lined chamber and bore, phosphate coating. For the best part, they will provide the non-F marked correct front site base for an A1 A2 upper.

$275 roughly. The colt is $325 but no delta ring and F marked Front site base.

12

Interested to hear about the Rosco. We’ve been getting off the long range and going bang bang with frangibles on the pistol range lately. Been running my 10.5 FN barrel and 14.5 BCM SOCOM.