From Scratch SBR Build - Noveske, BCM, KAC, Colt

[Toyoland66]

This is the first AR that I built both the upper and lower. I tried to pick high quality parts to result in a reliable and KISS (in my opinion) defensive weapon.

Upper Specs:
Noveske MUR receiver
BCM 11.5 ELW Barrel
BCM Ion Bond BCG
BCM Ambi charging handle
KAC URX4 10.75 MLok Rail
Noveske gas block, BCM gas tube, A2 FH

Lower Specs:
Noveske Gen1 receiver
KAC trigger guard
Vltor A5SR RE, A5H2 buffer, Vltor rifle spring
Noveske endplate
Norgon
BAD ASS safety selector
ALG QMS
BCM mod 0 grip, B5 bravo stock
All other lower parts are colt

Other:
KAC 300m rear BUIS
DD fixed front BUIS
Surefire X300 in exo mount
Aimpoint T1 2moa, Larue 660, IO Cover, KAC battery cap
BFG vickers sling with sewn in QDs









Pics of build









I used a BEV block in a hitch mounted vice to assemble the upper.

This lower originally had a basic BCM 11.5 upper on it (the upper with MOE handguards in the photo above). I SBRd a second lower right before 41p with the intentions of building a MK18 clone. I was going to buy a 6920 upper and chop it to 10.3 but decided to build a second 11.5 upper instead.

I shoot rifle left handed so ambi controls are utilized on all of my rifles. I have standardized on BAD safeties, norgon mag releases, and BCM A44 charging handles. I had the DD front sight/ x300 combo on a 13.5" rail on another rifle and felt it was too far forward, it's perfect on the 10.75 rail.

The URX4 was chosen for multiple reasons, the 10.75" length puts the end of the rail right at the back of the flash hider, the integrated barrel nut design results in essentially a monolithic upper, plus I really like KAC rails. The install is pretty straight forward, it clocked like it was supposed to with the shims specified. The two quirks are that the gas block installation is difficult since it has to install after the rail, the rear set screw wasn't accessible through the mlok slot but I was barely able to get it with a ball end Allen key. The second issue is that you can't use barrel blocks to install the flash hider, I was nervous tightening the A2 with crush washer using the Bev block but had no issues.

The ELW barrel was chosen for the optimum lightweight profile, the noveske gas block was chosen over BCM because of its smaller profile.

The MUR upper and ion bond BCG were "why not" upgrades. They didn't add much additional cost but theoretically are upgrades. I chose the Noveske MUR over the standard MUR since I am running a Noveske lower and because it has extra meat at the front of the receiver, since the URX4 doesn't have anti rotation tabs there's no interference issue and I think the combo looks better aesthetically.

I think most of the other parts I chose are pretty self explanatory, I went with proven components and nothing exotic. The gun shoots great and I am really happy with it.

[npthaiduong]

Very nice build. Can you share how much it costs you in total? I am working on my 1st SBR project too.

[Toyoland66]

Without doing a spreadsheet I would estimate somewhere around 2k plus the stamp and optic, so around 3k all in.

The nice thing about building from parts is being able to spread the cost out over time.

[scooter22]

Nice!

I'm surprised that you were able to properly install the GB under the URX4. Any up close pics of the GB screws?

[Jwknutson17]

Nice!

I'm surprised that you were able to properly install the GB under the URX4. Any up close pics of the GB screws?

Pending how close you can get the rail to the upper you may only have to take very very little off the Mlok slot. Ones that have a larger gap, you then have to take out more material on the rail. The 10 inch rails do not have this issue on car gas systems. All of the ones I have assembled I took out some amount of material to properly install the GB.

[Jwknutson17]

Op. Excellent build. What TQ value did you get to on that rail? Assuming that picture is with it hand tight? Typically you want it closer to the 12 then you have it. Think of the edge of the upper rail dead nuts in the center of the rails 12. And you get to 60+ with that small amount of movement. I would assume if you had it hand tight in that location you would be well into the 120+ range. Some of the early examples I had, had install TQ values printed from 60-140 ft lbs. I believe the newer install instructions have less of a printed spec value.

[Toyoland66]

If I have to mess with the GB again I will drill/ slot the rail for better access. The BCM barrel has a healthy dimple and I was able to get it tightened with the ball end hex basically maxed out. The .625 gas block probably helped slightly with that angle. The screws are installed with rokset so I am not going to mess with it unless there's an issue.

That's good info on clocking the rail, you are correct that is hand tight and per the diagram I thought was at 11:00 as instructed. I used the shims specified based on where it clocked handtight with only the black shim installed. I didn't use a torque wrench to install, I have one but thought it wasn't necessary, from what I had read about the urx4 being torqued based on angle rather than torque value. I read as much as I could find on the install but didn't find a whole lot other than Jack's YouTube video. Hopefully the next guy who installs one will read your post before attempting.

It does shoot well so I guess the upper end torque will be ok, I know lower torque values are typically better for accuracy. It shoots 4" groups at 100 using 55 gr xtac and the 2 moa T1, which I think is pretty acceptable for the intended use.

[Jwknutson17]

I wasn't really worried about the value more then just curious from the ones I have installed. That's all. Excellent build and have fun with it.

[mballz23]

How do you like that 11.5 ELW?

[Toyoland66]

I haven't put it through its paces yet but so far I like it. An interesting note is that a 11.5 govt profile is .625 under the handguards. I can't think of anything that is sacrificed with the elw compared to a govt profile barrel especially with a barrel this short.