The Definitive Colt MK18 / CQBR SOPMOD Block II Build

AR/M4 Custom Build Forum
1

Decided to go all out and do a clone correct SOPMOD Block II MK18 / CQBR. Little did I know it would take over two years to collect all the bits and pieces. Although there are some things that I would really like to change out (I’m a lefty), I decided to stick to what I believe are the most commonly issued parts for this platform. Hopefully, this can be used as a reference for others interested in taking the same path.

Base rifle:

  • Colt LE6920 (M4 CARBINE marked)

Lower swap:

  • I later replaced the Colt LE6920 lower with a Colt LE6920SOCOM (M4A1 CARBINE marked) one, as it is more clone appropriate.

Upper:

  • Upper receiver - Colt LE6920
  • BCG - Colt
  • Reliability kit - BCM extractor spring, BCM extractor spring insert, BCM o-ring
  • Charging handle - PRI M84 Gasbuster
  • Barrel - Colt LE6920 (cut to 10.3" w/ gas port opened to 0.070" by ADCO)
  • Gas Block - Daniel Defense MK12
  • Gas tube - Colt
  • Flash Hider - Surefire FH4P Model No: FH556RC-1/2-28
  • Hand guard - Daniel Defense MK18 RIS II (FDE)
  • Forward Assist - Colt (tear drop)

Upper Accessories:

  • Front BUIS - KAC RAS Front Folding Sight (99051-TAUPE)
  • Rear BUIS - KAC 300 Meter Flip-Up Rear Sight (97082)
  • Rail Covers - Magpul (FDE)
  • Vertical Fore Grip - Tango Down (ITI) BGV-ITI (FDE)
  • Sling mount - CQD
  • Weapon Light - L-3 WMX200 (VBL-000-A27)
  • Optic - ELCAN SpecterDR™ 1-4x 5.56 (FDE)
  • Optic (Alternate) - EOTech EXPS3-0 (FDE)
  • Suppressor - Surefire SOCOM556-RC (FDE)
  • Target Pointer / Illuminator / Aiming Laser - L-3 - Insight Technologies ATPIAL-C, AN/PEQ-15 (FDE)
  • ATPIAL/Weapon Light Dual Switch - L3 - Insight Dual Button Remote (FDE)

Lower:

  • Lower - COLT LE 6920 SOCOM (M4A1 CARBINE marked)
  • Lower Parts Kit (LPK) - Colt
  • Trigger - Geissele SSA
  • Grip - Colt A2
  • Endplate - CQD
  • Receiver Extension - Colt (4 position)
  • Castle Nut - Colt
  • Buffer - Colt H2
  • Buffer Spring - Colt (carbine)
  • Buttstock - LMT Enhanced SOPMOD Gen I (black)
  • Buttstock (Alternate) - LMT Enhanced SOPMOD Gen I (FDE)

Misc:

  • Sling - VTAC 2 Point - Padded (AOR-1)
  • Magazine(s) - Magpul PMAG M2 30 rds. (FDE)

This has been the most fun I have ever had on a build and the end product has been utterly reliable. I will note that it is a bit heavy compared to my other SBRs but for this build, I wouldn’t have it any other way!












2

Looks awesome man… dang you’ve got a ton of money invested in that thing!!!

3

Thanks!

I did a spreadsheet after I was almost finished and about threw up. I didn’t pay full retail for everything but this will give you a good idea of how much you could sink into one.

4

Looks great

5

Nice Rifle:cool:

6

That spreadsheet hurts me lol… Now the question is: would you do it again?

7

Definitely! The MK18 / CQBR goes in the Gun Hall of Fame in my opinion. It’s iconic.

8

Yeah. It’s a tough one. You can shave 5 grand off without the Elcan, SF can, and PEQaroo! :wink:

9

That’s the beauty of this style of build. You can be totally clone-correct at around $2500 and add parts/accessories as your budget/needs allow.

10

In order for it to be an exact clone the PRI gasbuster would have to be broken.

Honestly, looks great.

Rick

11

Finally received my SOCOM556-RC and got to play around a little at the range. I’m very impressed with the lockup mechanism… I also learned that the rear BUIS needs to go when running the ELCAN. I don’t know how people shoot them moved forward on the upper. With my KAC 300m mounted behind it, my teeth were pretty much biting the charging handle.

Next up is a MRDS mounting plate in FDE and a Docter!

12

How/where did you get the 4 prong FH?

That’s an excellent build BTW. The gold standard for what I’ve seen in MK18s.

13

I kept my eye on TOS EE for about 6 months before one popped up. From what I hear, the SF3P is a better muzzle device but the SF4P is “correct”.

14

I’ve got the older version which is the 215A. The SF3P doesn’t even come close as far as flash suppression is concerned. The larger three prongs might be stronger, but don’t perform like the four prongs.

15

$2500 still seems like a lot at first glance… but I remember doing the math on my 10.5 build with an Aimpoint… And it was right in that range.

16

More pieces to the puzzle arrived today. I picked up an Elcan MRDS mount (FDE) and Docter MRDS as these are considered “clone-correct” additions. To be honest, even though I have had it for quite some time, I really not feelin’ the Elcan. Every time I mount the EXPS3-0, I am amazed by how much faster it is (and how much lighter the complete package becomes).

17

Annnnndddd there’s my dream build… envious. Looks amazing!!!

18

I love everything about this thread. And will make me covet my inbound mk18 upper even more.

19

Where are your tie-downs?

Just start pushin.

Nice build. All joking aside, I feel that the black SOPMOD is definitely the more commonly issued stock. I don’t believe I’ve ever actually seen a toupe one in the wild (not saying they don’t exist). From what I have seen, they are usually black or painted. I feel that the tan stock mostly came about as a builder’s option, trying to balance the color of the rifle a little more without the rattle-can. We also generally get stuck with the Matech rear sight, who knows why.

Looks great. You obviously spared no expense, and the QR code is a nice touch.

20

Thanks for the feedback on the stock. I have a black gen 1 LMT Enhanced SOPMOD that I usually run on it and I should probably retake the pics with that stock installed as it is more true to the original. I think I am going to wait on the PEQ-15 to arrive from TNVC before I do any more glamour shots.