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

Honestly never measured my pistol. I have a 10.5 on a pistol lower with the SB brace.

My brace isn't seated all the way on the tube, it's backed out an inch or so from being pressed full on. Not that I care about the length but  I'd assume one would measure from the end of the buffer tube to the end of the barrel and not wherever the brace was placed on the tube.

Which buffer tube is that?

Correct, end of the barrel without the muzzle device (unless it's perm attached) to the end of the buffer without the brace.

There was an ATF response to an email a while ago where the ATF said you would include the length of the brace in the same way you would measure an SBR with the stock fully extended but it was the ONLY time I've ever heard that opinion, normally its without the brace as its not really permanently a part of the pistol or firearm.

Brownell's has had the colt ambi selectors in stock for a few weeks now for $46.99, full auto version, that's where I got mine. Full auto works just fine in any semi auto without issues. And it won't make yer gun full auto in case anyone curious.

Eta photo- colt ambi from brownell's. Long/short levers

I've been on somewhat of a retro clone block 1 flashlight kick. All have been found on the EE.



Got this one from a member that regularly posts here and in the m4 pic thread. I was happy to learn that this is the most rare and hard to find body style in the m951 series. It is the earlier body (sometimes referred to as gen 1), includes the sw02 tail cap, and is in decent shape considering its been issued.  Question, I've been trying to find the difference between the m951 and m952 and so far all that I have found is that the m952 has a differen mount and better mounting options available. Is that the only real difference?

I went and got another mk18 started. This one will have an fn barrel with fsb and I have an fn upper that I'm gonna pair with it. If I can find a fsb mk18 ris or a fsp m4 ris cutdown for it, would it still be considered block two since it has an ris ii?  I wasn't sure if the fsb made any difference in determining b1 or b2 or if it is just the ris ii vs ras. I had the newer fn setups in mind as shown by cd, only this is not socom profile and has the fsb.  This one will be rattle canned for sure. Pics to come next week. If anyone has a lead on a cutdown m4 ris ii send me an IM. Otherwise I may go ahead and do it myself as I have been seeing the fsp m4 ris ii's in the $350 range.

Ris 2 would make it a b2, kac rail with b2 accessories phases replacement 1.5

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Lmao.

I’ve moved on from the tanodized g33 to my skinodized wmx200.

951 would have the thumbscrew style mount and 952 would have a QD mount like an ARMS on earlier ones and the Surefire QD on more recent ones.  Both bodies are the same so aftermarket mounts should work the same whether it started as a 951 or 952.

Gotcha. I spent a good while tryin to research the difference, and from the pics, I couldn't see any difference except in some cases their was an arms mount or other. With the parts bein interchangeable I'd think I was on to somethin, then I'd find an example that would disprove what I thought. Are the m961vs m962 similar in that respect or do they have other noticeable differences?

Nice. Not too many greens seen on here. Color makes sense for my geographic location since its green half the year, and white the other. I'm sure a snow camo/white Mk18 wouldn't be looked upon to favorably though I just may end up doin one with some xtra parts for shits n giggles. We'll see.

There have been pics of snow camo on CQBR's. Some SEALs training someplace cold and snowy a few years back, doing photo ops as per usual. I'm sure some kind gentlemen will post the pics. Looked pretty tight too. I've seen a few guys in here post their winter camo's too.

Should be the same for those also.

Thanks for the information and replies.  Here are a couple glamour shots to keep the pics flowin. I just got an awesome deal on a cutdown m4 ris ii so I will have a block ii to post real soon. I'll need to track down the barrel nut wrench for it. And damn, just realized I'm gonna need a block ii optic as well. I've seen block 1' s with block 2 accessories, but what about block 2 rifles with block 1 accessories? I'm sure they're are lots out since  the combos are infinite.  I've wanted a ta31f for some time now. I suppose I'll have to use my tax refund to get one.

Thanks.  I did it to be different.  Also, FL is green year round.

Alright, so no kind gentlemen showed up to post them, so here you go:

Bad. Ass.

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Oooohhhh.....kind of want.  I've been buying the AR Stoner Ambi selectors from Midwayusa.  They work great, but the problem is both levers are full length.  It would be nice if they made one short one long like the Colt units.

Some more parts showed up, waiting on the ambi colt selector and DD wrench to finish building this into a functioning upper. Next step, optics. Attached File

Nice. I'm really likin that.  Looks I'll be doin a summer and winter block 2.  I wasn't sure what I'd think about a snow camo version, but that's pretty slick.

Can you post your 100m groups when you can? Non magnified is fine. Someone was trash talking 14.5" barrel grouping at 100 yards. I tried to explain 14.5-20" is not significant until you hit 600m. Also interested in where you got the FNs and how they group.

Who are you talking to?

Went for a conjugal visit today to test the can on the 10.3, sucks having to go home without it but at least i can shoot it while i wait.

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What mount are you rocking on that Surefire?

Looks sick broham. I'm diggin' the two-three tone SF weaponlight.

Anyone got a lead on some decent brownell's discount codes? I remember around Christmas time there was the 30 % off plus the active junkty discount. just might pull the trigger on one this time if I can get it in the high $600 range.

Looks like a vtac micro hub.

Its a unity tactical fusion hub. Misty useful with a peq.

Haha thanks, i always paint shit then decide to remove it but get to lazy to get it all.

One more pic because its monday

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Around Christmas they were going for $605 with a 10% coupon and 4% from AJ (but it was on sale for $699.99). The current codes aren't all that great - max is $20 off. I would suggest signing up for Brownells mailing list because they often have single day 10% off coupons that can be easy to miss if you don't check the site daily. Also, keep an eye here:

https://gun.deals/content/brownells?view=list

That is a regularly updated list of all the coupon codes - both advertised and not. Brownells almost always has unadvertised coupons good for $10 off $100, $20 off $200 or $30 off $300. They tend to be a bit more stingy with their 10% and other higher value coupons.

Has there been any discussion in this thread of if the existing SOCOM contract will be the RC or if it will be the RC2 after the new one Surefire was awarded? I apologize if it was discussed before.

The current contract is for the RC. There has been no new solicitation for a replacement. The RC2 would not be correct for these clones.

Thanks boss.

My Block 1...

Perfection!

I know it’s somewhere in the 964 pages but I can’t seem to find it..

What overall length did everyone put on their form 1 for their MK18 Mod 0? I am sending mine off tonight and have not gotten my barrel chopped yet.
Thanks and looking forward to finally being able to post in here.

Depends on the stock if you want to be exact. I put 28" for my 10.3" CQBR, which should be pretty close when using a Colt N1. A SOPMOD would probably be 29"? Since you can't very well assemble it to take measurements, anything in the ballpark should be fine. You can always amend it later if you want to be exact.

I put 30" on mine with a SOPMOD.

I put 29.3 with a SOPMOD stock.

Happy block 2 Tuesday. I just received my first 99051 today. Bought off the EE for a decent deal. This one has a nice caramel chocolate color. The pic in the ad sort of gave it the stone color that was around for a while, but this pic is more representative of the color it is. I'm happy with it. I was surprised at how light these are.

Thanks fellas. I put 29” as i will eventually replace the waffle with a SOPMOD. Debating between an LMT or B5 but I know I’ll end up with the LMT cuz cloning.

One of the good FDE ones. I'm not sure if the new ones still have that diarrhea greenish/tan cerakote color or not but those ones were hideous. The chocolate FDE is where its at. And the black ones

I agree. The last time I saw a newer one (in pic) it still had that Cerakote look. I was contemplating going black (insert joke) since it's really hard o tell the actual taupe tone from a pic, but the price was right with this one so I took a gamble. I figured I could always paint it if arrived lookin like baby diarrhea.

Thank you. I was tryin to find that page but I somehow erased all my bookmarks. I kept findin pages with codes that were expired or just didn't work.

Eta- also had this waitin for me when I got home. Not sure what I'll end up doin with it, but the price was too good to pass up.
FN barrel (not socom but eh), Cqd rear, LMT gen 1 black, y/m bcg, Kac ras. Bought painted so I'll eventually strip and use to try out diff color combos.

Same length I put on my F1 for my Mod0 as well. Also, if doing a mod0 get the LMT gen 1. I managed to find one in the EE brande new still in the wrap a while back.

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My addition to the Mk18/M300 thread.

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