When discussing the Mk 18 / CQBR program, we can divide the history and discussion in to two distinct categories: 1) The weapon system itself / upper receiver supplied and 2) the group of accessories deployed on said weapon systems (SOPMOD).

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Mk 18 Mod 0 / CQBR

The M4 carbine and M16 are not ideally suited for all missions, so it was proposed that the modularity of the M16 series would allow a user to replace the upper receiver of an existing weapon with one more suitable to the task. One of two proposed special mission receivers that were planned for inclusion into the SOPMOD Block II kit, the CQBR has taken off on its own. Like the proposed Special Purpose Receiver, the Close Quarters Battle Receiver has been more or less taken on by the Naval Surface Warfare Center, Crane Division (often referred to as NSWC-Crane or just "Crane") as its own project following the CQBR's removal from the SOPMOD program. Just as the Special Purpose Receiver morphed into the Special Purpose Rifle, and was type-classified as Mk 12 Mod 0/1, the complete CQBR-equipped carbine has been type-classified as the Mk 18 Mod 0.

The purpose of the CQBR remains to provide operators with a weapon of submachine gun size, but firing a rifle cartridge, for scenarios such as VIP protection, urban warfare, and other close quarters battle (CQB) situations. The CQBR is designed to provide improvement over previous AR-15/M16-type weapons in this category. The CQBR is usually issued as a complete weapon system, and not just an upper receiver. The CQBR was once only available to Naval Special Warfare units, but the Mk 18 Mod 0 has become general issue for Visit, Board, Search, and Seizure (VBSS) missions and, as of 2006, for NCIS agents deploying to active combat zones.[citation needed] The Mk 18 is also used by the Coast Guard's Tactical Law Enforcement Teams, Maritime Safety and Security Teams, and Maritime Security Response Team and the United States Navy's Explosive Ordnance Disposal (EOD) Operators.

Wikipedia has a good article with sources on the original CQBR/Mk 18 Mod 0 and its development.

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SOPMOD

The SOPMOD Program Management Office at NSWC Crane, IN, provides standardized, versatile weapons accessories to meet needs across SOF mission scenarios. These accessories increase operator survivability and lethality by enhanced weapon performance, target acquisition, signature suppression, and fire control.

The CQBR itself was originally part of the SOPMOD program as an accessory replacement upper receiver for the M4. However it was eventually separated out into its own project.

SOPMOD accessories for the M4/CQBR originally included things like the KAC RIS/RAS, SOPMOD stock, KAC M4QD suppressor, AN/PEQ-2 illuminator/laser, ECOS-N red dot, ACOG, etc

The SOPMOD program has gone through multiple minor and major evolutions throughout its lifetime. The most significant is commonly defined as "Block II" and included the introduction/replacement of accessories that met the updated needs of operators. The most visually significant "Block II" accessory is probably the replacement of the KAC rail/FSB with the  Daniel Defense RIS II free float rail with low-profile gas block. Other updates include things like the Surefire SOCOM sound suppressor, EOTech RDS (553/SU-231 & EXPS 3-0/SU-231a), LA-5/PEQ ATPIAL, etc

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Link to docs and photo albums

 Presentation on CQBR from Crane
 Operator's Manual for Mk 18 Mod 0
 SOPMOD Program Overview presentation from Crane
 Photo Album of Mk 18 Mod 0
 Photo Album of CQBR with SOPMOD Block II accessories

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Because of the long history of both the CQBR/Mk 18 and SOPMOD programs, it's common to find weapons with various mixed configurations in the field, all depending on what time and unit the weapon system belongs to. Below are a few examples with descriptions to illustrate this.


Example of a Mk 18 Mod 0 in as-issued configuration including: M16A1 surplus lower receiver, SOPMOD buttstock, KAC RIS, KAC M4QD flash hider, Aimpoint Comp M2 in Wilcox mount, LMT rear fixed sight, CQD rear sling plate.


NSW Operator CQBRs with original SOPMOD accessories including KAC M4QD sound suppressor and AN/PEQ-2 IR Illuminator/Laser.


Member of a Combat Camera team with a CQBR with KAC RAS and M4QD flash hider but with other updated accessories from the "Block II" SOPMOD kit including SU-231a (EOTech EXPS 3-0), EOTech G33 Magnifier, LA-5/PEQ ATPIAL, Insight WMX-200.


Good example of "early" CQBR with SOPMOD Block II accessories including SU-231 (EOTech 553) and SU-233 (Insight M3x weaponlight).


Example of a more "modern" CQBR with SOPMOD Block II accessories including the updated SU-231a (EOTech EXPS 3-0) and Insight WMX-200 weaponlight.


Many times certain configurations are common within certain branches/groups. Here a Marine Raider is seen with a CQBR with an AN/PEQ-16 (USMC issued vs. the LA-5/PEQ SOCOM issued ATPIAL) and KAC NT4 suppressor (vs. the current Surefire SOCOM suppressor).

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Building a clone

If you're interested in building a "clone" of a Mk 18 or CQBR equipped M4A1, here is a basic parts list to use as a guide and get you started. This list is not exhaustive and see the * note above regarding personalized accessories.

                       | Mk 18 Mod 0                      | M4A1 CQBR Block I                   | M4A1 CQBR Block II                                      
Lower Receiver         | Mil-spec forged A1               | Mil-spec forged A2                  | Mil-spec forged A2                                      
Stock                  | Gen 1 SOPMOD (Black)             | M4, CAR, SOPMOD, CTR & others       | M4, CAR, SOPMOD, CTR & others                            
Pistol Grip            | A1                               | A2, ERGO & others                   | A2, ERGO & others                                        
Rear Sling Plate       | CQD                              | CQD                                 | CQD                                                      
Upper Receiver         | Mil-spec forged M4 profile       | Mil-spec forged M4 profile          | Mil-spec forged M4 profile                              
Barrel                 | 10.3"                            | 10.3"                               | 10.3"                                                    
Rail                   | KAC RIS                          | KAC RAS                             | DD Mk18 RIS II (FDE)                                    
Rear BUIS              | LMT Fixed                        | LMT Fixed, MATECH, & others         | MATECH, KAC 300m, & others                              
Front Sight            | A2 FSB                           | A2 FSB                              | KAC 99051 BUIS (Taupe)                                  
Front Sling Attachment | FSB Sling Swivel                 | FSB Sling Swivel                    | CQD                                                      
Muzzle Device          | KAC M4QD                         | KAC M4QD                            | SureFire FH-556-RC                                      
Supressor              | None                             | KAC QDSS NT4                        | SureFire SOCOM556-RC (FDE)                              
LAM                    | None                             | PEQ-2                               | LA-5                                                    
Weaponlight            | SureFire M962                    | SureFire M952, M962                 | Insight M3X (Tan), Insight WMX200 (Bronze)              
Optic                  | Aimpoint Comp M2 in Wilcox Mount | Aimpoint Comp M2 in QRP Mount, ACOG | EOTech 553 (Tan), EOTech EXPS3-0 (Tan), ELCAN 1-4x (FDE)

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Link to previous threads

 Previous Mk 18 / CQBR Thread Part I
 Previous Mk 18 / CQBR Thread Part II

Only the Mk18 rail and to cut the barrel down.

CD

Is $300 a good deal for a used tan 553 marked su-231? The marking is faded. Can you stil get it refurbished? Found it stashed at a local gun show.

Cheaper than I'd let mine go for.

One step closer, picked up a front sight.

Beautiful coloring!  LOL

Seriously, i'd like to find one with that tan shade.

9line velcroed on. Never pulls. Same stock I use deployed. But without t used to pull like hell. That vltor stock and all...

Guy I bought it from probably has a few more I could pass his info along if your interested. It was about 195$ shipped, came still sealed and in the original box.

@OilfieldTrash78

What spring and buffer? You should probably be using a Colt spring and H3 suppressed with 5.56.

Should I rock the DD upper ( Matches very well surprisingly...) or wait for a similar colored colt upper to pop up on marketplace?

I am running a H2 and standard spring...guess I need to step it up.

Get a Colt upper. Bonus points if it doesn't match.

Plus it's only a matter of time before it gets rattle canned

Guess I'll be selling the dd components and on the hunt :P

Uncles guns 14.5/10.3" suppressed/non all use a H2 and standard carbine spring.


CD

What kind of ejection pattern do you guys see?

I'm at about 1 o'clock suppressed with m193 running h2 and a standard spring. 100% reliable suppressed and unsupressed 

H2 is currently clone correct, but that doesn't mean it is the best choice for his rifle.

If you have an H and an H2 you can make an H3 to try out. I personally make sure my rifles lock back not just on 5.56 but also on Federal .223 55 gr so there is a little extra gas.

Don't forget the smaller gas port on issue/correct barrels.

You're welcome 

#.070mafia

Oh boy..wait for it......wait for it.......

Specialized Armament has them.

Don't bother trying to call, just order it and wait.

Best place to get a PRI gas buster?

Oh, I know...I am running one of the .070 barrels...just wanted to make sure mine was running right after swapping from my commercial DD barrel

New "beauty" shot.  Forgive my crappy skills....

So I ended up getting a used 553/SU-231. Got home and cleaned it with some windex/hoppes, and the "SU-231/PEQ" marking was not worn/faded and came out brilliant. My question to anyone that has one of these, my battery cap and hood do not have any sort of Eotech markings other than the yellow laser sticker. Is the typical or this a special version? Thanks in advance for info.

Guys with risers, which ones are you running? I know Wilcox has one but I don't have the Eotech magnifier so I won't spend that on the riser without it. I like to shoot "head up" especially with my nods. I found the Weaver Tactical online for about $50. Just wondering what you guys are running

I was told by the guys at TNVC that the A3 is a better unit than the APTIL-C in terms of features if I remember correctly.  I got my A3 back in 2015.  One feature is that you can zero your visible laser and it will zero the IR laser at the same time.  I also believe the Ir illuminator on the A3 has more adjustments than the APTIL-C?  I got the A3 mainly because the APTIL-C was out of stock and I wasn't into clones yet.  Call TNVC and speak with them.  They'll set you straight.

The APTIL-C is clone correct unless you can get your hands on a PEQ15a (never seen one for sale) or a real PEQ15 (run about $2000?) or LA-5 ($3000?).

I don't think there is a clone-correct one per se, but I'd try to stick with a quality manufacturer. We have seen the LaRue LT100(?) used on both M4s and HK416s, the KAC has been spotted on a variety of guns, and I have seen a super-high A.R.M.S. riser (#54, 1.5" rise ) used on old-school CQBRs with EOTech 551s/552s (check out the Instagram profile for sofsurvivor). Those are all going to be pricier options. TannerB posted a pic on Instagram showing a Leupold riser that looked pretty nice and is a bit less expensive than the KAC or LaRue.

ETA: here's a pic of the 1.5" riser (on top of a SIR no less)

That means it's a legit SU-231. Mil 231 and 231As do not have any other markings other than the designation. No L3 or EOTech logos.

A bit OT but I received my 80% lowers back from anodizing and had no issues. So hopefully that "problem" is currently only local to USA.  Does anyone know what the outcome of that ordeal was anyway? It seems the thread was nuked from the legal section.

The OP was going through and deleting his posts, so I would assume he probably had a MOD nuke it so there wouldn't be anything to use against him should he have to go to court over it.

Pic thread:

There's a PEQ15a on the big auction site right now it appears - I don't know enough about them to know if legit...  shipping from Russia?

looking good!! what mag is that??

Finally replaced the A2 flash hider.

That's kind of what I figured and probably a good idea.

Great pics!

ITAR bro.  I'd avoid that shit like the plague.

Thanks!  They are D&H FDE mags.  The blue on the bottom is painters tape.  I use a sharpie to mark what's in them.

Yeah I have seen that one.  I think it has constantly been for sale for about 2 years now ha.

Check out DSG...  They are a site sponsor.  If they are out, it is never long before they are back in.  They also have the CQB plates, which everone seems to have a hard time finding...

Looks fantastic. Love that simplistic old-school look. How did you get your faux 3rd pin to stick out like that, contrast wise?

Eta: pic with wrong muffler

Attached File

PSA had a good deal on all sizes and colors. I picked a few up at one point for some bros in this thread.

As far as PEQ15's you can track them down for $1000 - $1300 every now and then.

Silver Sharpie then rubbed it a bit with my finger to dull it.

ETA: It really doesn't stand out as much as that pic would suggest. When I adjusted contrast and whatnot, it made it stand out a bit more.

Silver Sharpie, copy that.. heading to the store!

Probably one of the "Law Guns" Eotechs still floating around.  I WOULD NOT send it in to Eotech as they'll most likely confiscate it as stolen .gov property.

ETA:  Read more here.

Is that Saker painted or cerakoted?

Rustolium'd Omega. It's a wee bit more baked since that pic. It's a fantastic can, but embaresed to show it in here.

Did Colt ever assemble factory CQBR uppers? I saw this in the EE Colt factory CQBR uppers for sale

I want the flashhider!

10.3 by J S, on Flickr
10.3 by J S, on Flickr

I get that some of the parts are rare, but $2000?  I picked up a clone correct upper with all of the same parts for $1200 not even a month ago.  I hope nobody pays into that sham.

They definitely did not. No idea what he means by "factory built". Either they're just personal builds or "fell off the back of Crane's truck". Something's very fishy. Either stolen goods or the guy is lying.