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

Could blast it and re-ano but that's a lot of work lol.

I'm pretty sure my SU-231 markings were laser or acid etched and not engraved, but I suppose you could color fill the engraving white.

Can you buy blank replacement hoods?

Mine is lasered as well.

CLW does it with a laser, so maybe engraving is the wrong term. He refers to it as "engraving", but it comes out the same as the UID plates: white laser etched text and UID block.

Oh alright yeah that's laser etching. Engraving is just removing material. (Like Braceman does on our lowers)
That's pretty cool that they use the correct method. I was wondering why someone would want the markings engraved as it would just be the same color as the hood (or base for 553).- bare metal

That's pretty fucking slick rick!  Have we got any photos of the correct markings/placement on the EXPS?

Honestly don't know.  Where did it come from? ie FN M4 series of carbines or PSA, as they use some of their bbls.

CD

Here are a few:

That looks like a gun I need to see more pictures of!

Law Tactical folder on a MK18/CQBR... yay or gay? Works awesome with the Shockwave Blade while waiting on a stamp in the meantime.

Apparently you can trade a 250cc dirt bike for it ;p.

http://www.armslist.com/posts/4462186/birmingham-alabama-rifles-for-sale-trade--ar-15-w-eo-tech-trade-for-motocross-dirtbike

Hmmm....That's right in my neck of the woods. No dirtbike to trade though.

ETA: I see that's an old listing.

Nice! That FDE MRE rail is sweet

Why not just get one of the new ones? The new ones are good to go, I have one and the thing is BRIGHT and the spill and throw outdoors is great!

That one recently got traded for a Knight's LW URX. I do still have another I'm going to do a build with soon! I'm just lazy and haven't put it together

Here's what mine looks like. No eotech markings.

Yours is marked the same as mine. According to Eotech, any that are marked 231 are legit .mil.

Well...I did a sopmod, I did a mk12, so naturally where else would I go but to a mk18!? It is an on progress bit, and obviously being built as a pistol...but here she is so far...rear sight is on the way and I am debating putting the aimpoint from my sopmod on here, and slapping a sig Romeo 5 on the sopmod...or I just find another aimpoint for this lol. I'll update with some fresh pics once the rear sight shows up and I decide what to do with the optic.

I have one of those weird marked eotech things just collecting dust in safe, damn.

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Lol I'm surprised you still have that thing. Then again knowing you, you've probably had a good 15 of them since then and that's just the most recent.

Ol' dusty faithful.  Been taking up space since 2014.

In all reality though, I almost wan't to do another clone with it.

I think it and that there 16B would be better off on another clone than collecting dust, but that's just me.

That was my original thought as well, but have been reading some so-so reviews on the new version...  But yeah unless I run across a nice deal I suspect I'll just wind up with newer model...

Oh. Well maybe it is better off collecting dust. Assuming you want to use white light.

I didn't realize Carolina LW would add SU markings... I'm considering getting it done on my old logo EXPS, and picking up some UID tags too.  But, is there any concern that adding mil specific markings, uid tags, property of us govt, etc to a rifle could be an issue down the road, for whatever reason - ie why does civilian joe have this mil property marked rifle, is it stolen property, anything like that?

I don't think this is entirely true. I used to have one I bought way back in like 2010-11ish.  Bought new from a vendor, brownells or midway I don't remember.  Certain serial numbers I want to say under 700,000 could be mil, anything over that could be civ.

Nice rig.  This is my favorite setup.

Unless you get a blank hood it will still have the regular Eotech markings that the real su231a's don't have.

Yep. Mine was purchased directly by an individual as well. But what squirell said is what EOTech actually thinks sadly. More EOTech retardation for ya

I doubt it would be an issue outside of Eotech. No different than my 80% lower that's marked US Property and with the same s/n of my issued rifle.

Just relaying what I was told when I contacted them. I've seen several retailers offer SU-marked units and even seen them in person at a LGS. I told that CS rep that and he said that was not possible and wanted to know where I'd seen them.

Maybe he was a newby and just assumed anything .mil marked was .gov property.

Yes, I know, I have been there dealt with that.  One guy I called didn't seem to know and just said if it had that marking it was mil. I had to kindly remind him that I purchased it new from so and so place and he then got back to me saying "well it has to do with serial number 700k or whatever being the cutoff for mil so if it is above that, it's more than likely civ.

It's really no big deal just saying what the guy said, it's been like 4 years since I asked lol.

Yes that's basically what it is, they are just assuming.  Have them run the serial and they likely see it wasn't.  Just depends on who you get on the phone i'd guess.

I think more than likely a noob got confused with the 231A marked only being sold to mil, with the 231's having the same story. Which we all know is false. They should really get a clone guy in there running things. I would volunteer myself, but I'd probably lose the job within a week for making it rain free EOTech's in the CQBR and B2 threads.

They had a clone guy in there LOL.  He joined the Navy instead.

What's his username?

I don't remember, But I think he's active in CRA.

LMAO

I have had two SU231 marked 553s serviced without issue.

One was for sure a Law Guns purchase too, before I knew what that meant . They noted on the return form that it had been serviced as "State LE Property" and returned.

You got lucky , shortly after that fiasco they realized what they were and stopped returning the lawguns optics that people were sending in.

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Any way I can get mine cleaned up a bit? I think the guy who etched mine was a little drunk.

In other news:

Attached File
Attached File


And its not pictured, but I just got the Geissele trigger in the mail yesterday, and I have a KAC front sight in the mail. I'll probably order a KAC rear and a TD grip soon, and then I think the upper is done. Then I can work on making my lower game not suck so much, lol.

Is the QD TD foregrip clone correct? I hear the regular ones are hard as hell to get on.

More challenging than most to install, but once you get it going, it's cake.

JohnnyS,

Yes, have had them in the shop before.

CD

Always enjoy your builds, Johnny.

The installation issue with the TD grips and the RIS II is that the lower rail has to be removed to get it on/off (unless you get the QD version). The KAC slides on/off no problem (as you obviously noticed). The tradeoff, at least for me, is that the TD has storage and I like the Insight tapeswitch pocket.

Interesting.... My black 2007 SU231 was returned with a new blank base and the serial number printed on a typical label maker stuck to the side. I'm willing to bet the whole unit was replaced.