MK18 MOD1 Technical Thread

[Magic_Salad0892]

Some Mk. 18 Mod. 01 carbines use the KAC SPR Gas block, from what I heard.

I'm actually positive I saw a picture of one once. If I find it, it'll be posted.

ETA: Didn't know there was a second page when I posted this, oh well. At least now the manufacturer is listed. :I

[m249saw]

It just still seems weird that Cranes specs for the gas block is set screws.

I guess since its under the rail they arent worried about it getting knocked loose?

[scottryan]

Anyone else have any info?

[BBB]

The Mk18s/CQBRs are rare birds.

6 years in theater and other than mine and the ones my section ran (in 'stan) I've only run across one IA SEAL with one and one ODA with them in Iraq.

We inherited ours (6 I think) as CQBR uppers from our outgoing brothers.

I don't know where they all are, but you don't see many in Iraq or 'stan.

Whats funny is FFGs have these being used for VBSS ops. Go figure. Maybe the NAV thinks these shorties better used below decks rather than in the mountains of A-stan?

[decodeddiesel]

Good info.

[Magic_Salad0892]

Here's what I found on the errornet regarding Mk.18 specifications:

I found it on wikipedia, but I'm pretty sure it's copied and pasted from a Crane specs sheet I saw on said errornet a year or so back.

If I can find a .pdf file of the SOCOM block I and II accessories I will post it. As of right now the only one I have seen isn't up anymore. I will continue looking for one. But for now:


* CQBR type 1: Made from M4A1 uppers by shortening the barrels and opening gas ports, no longer produced, STD carbine buffer in use in host lowers at time of fielding.

* CQBR type 2: NSWC assembled with contracted and /or overhauled parts complete with all accessories to current standards at time of build, will work with H, H2 or H3 balanced to ammo requirements:
o H okay with M193/M855.
o H2 needed for MK 262/R2LP & will run M193/M855.
o H3 may be needed for an extreme case, or when the gas port is eroded but the barrel still groups.

* CQBR type 2A: NSWC assembled with contracted and /or overhauled parts, naked without any accessories or buffer. The buffer in the host carbine would be used or upgraded as necessary via the supply system same as type 2.

* CQBR type 3: Colt-contracted upper complete with all accessories. NO buffer supplied. The buffer in the host carbine would be used or upgraded as necessary via the supply system same as type 2.

* CQBR type 3A: Colt-contracted upper naked without any accessories or buffer supplied. The buffer in the host carbine would be used or upgraded as necessary via the supply system same as type 2.

* MK18 type 1: NSWC assembled carbine with contracted and /or overhauled parts complete with all accessories to current standards at time of build will work with H or H2 and could have shipped with either. Units will balance buffer to ammo requirements:
o H okay with M193/M855. (all ship board MK 18’s should have H buffers as this was the standard at the time of assembly).
o H2 needed for MK 262/ R2LP & will run M193/M855.
o H3 may be needed for an extreme cases or when the gas port is eroded but the barrel still groups.

* MK18 type 2: Colt-contracted carbine complete with all accessories H buffer supplied. Units will balance buffer to ammo requirements same as Mk 18 type 1.

* Upper and lower receivers: The lower receiver is a standard M4A1 lower receiver sometimes modified with the addition of a CQD RSM sling adapter plate. However, many CQBR rifles also use surplus M16A1 lower receivers. Internally, the CQBR also takes advantage of a larger gas port and modified bolt carrier and buffer assembly. The gas port has been opened to 0.070 in (0.18 mm). A number of Lewis Machine & Tool 10.5" (266.7 mm) upper receivers have also been reported to have been purchased for the CQBR program. These upper receivers feature a gas system optimized for short barrel use.

* Sights: Initially, detachable carrying handles cut down so that only the rear sight assembly was used. However, most of these have been replaced with the similar, commercially-made Lewis Machine & Tool adjustable rear sight. Also used are several types of reflex and magnified optics, most commonly seen is the Aimpoint CompM2 in a Wilcox Industries Corp. Picatinny (MIL-STD-1913) mount.

* Stock: A variety of M4 retractable buttstocks are used on a standard 4-position receiver extension, including the standard "CAR" stock. Most often seen is the SOPMOD stock, often referred to as the "Crane stock", created by Dave Armstrong of NSWC-Crane. The angled stock offers better cheekweld as well as providing two storage compartments for spare batteries. The stock must be removed from the weapon to access the storage compartments. The initial run of stocks was made by NSWC-Crane from glass fiber polymer. Because of this, they were somewhat fragile and did not always properly lock into the receiver extension. A rubber band was used to secure the latch so it would not slide out of the desired position. The current L7LA2B SOPMOD stocks are made by Lewis Machine & Tools and have none of these problems.

* Barrel: The CQBR uses a 1:7 in (178 mm) twist M4 barrel that has been modified in length to 10.3 in (262 mm). The diameter of the barrel under the handguards is 1.17 in (29.7 mm). The KAC M4-QD flash suppressor is fitted, allowing use of the KAC QDSS-NT4 suppressor (National Stock Number 1005-01-437-0324). Although it has a bayonet lug, the CQBR is not meant to be fitted with any fighting blades.

* Handguards: The standard handguard for the CQBR is the Knight's Armament Company Rail Interface System (M4 Carbine RIS; National Stock Number 1005-01-416-1089), which is designed for a variety of barrel profiles and allows for the use of any MIL-STD-1913 tactical accessories such as the AN/PEQ-2 infrared pointer, SureFire flashlights, or a vertical forward grip.

* Ammunition: The CQBR is designed to use standard 5.56x45mm NATO 62-grain M855 FMJ and M856 Tracer ammunition. However, due to the short barrel, the heavier 77-grain Mk 262 cartridge is preferred. There are no plans to rechamber the weapon in any additional calibers.

[C-grunt]

A little late but my buddy was using a Mk18 and has some pictures of his. Ill ask him if I can post them here.

[Bowser]

Mk18 is one of my favorite little carbines. Any more pics?

[polymorpheous]

I've bought a lower to SBR, saving the $200 now for the stamp.
Come tax time I will buying an upper for it.

Right now it comes down to the Noveske N4 basic 10.5", (bonus free lower!), and Daniel Defense's 10.3" Mk18Mod1 upper. (LMT may still be an option too.)

Now my understanding is that the gas port diameter plays a huge part in SBR reliability, especially when suppressed.

It is also my understanding that Daniel Defense is now a DOD contractor for the Mk18Mod1 uppers. However I've read that Daniel Defense gas ports are kind of all over the place.

I have one of their 14.5" CHF M4 barrels and it seems over-gassed compared to my buddy's LMT 14.5 M4 barrel. We both run the same weight buffer, and I have a A2X flash hider and he is running a Phantom. I can't see that making a big difference.

Any opinions on Daniel Defense's gas ports on these uppers?

[ra2bach]

I've bought a lower to SBR, saving the $200 now for the stamp.
Come tax time I will buying an upper for it.

Right now it comes down to the Noveske N4 basic 10.5", (bonus free lower!), and Daniel Defense's 10.3" Mk18Mod1 upper. (LMT may still be an option too.)

Now my understanding is that the gas port diameter plays a huge part in SBR reliability, especially when suppressed.

It is also my understanding that Daniel Defense is now a DOD contractor for the Mk18Mod1 uppers. However I've read that Daniel Defense gas ports are kind of all over the place.

I have one of their 14.5" CHF M4 barrels and it seems over-gassed compared to my buddy's LMT 14.5 M4 barrel. We both run the same weight buffer, and I have a A2X flash hider and he is running a Phantom. I can't see that making a big difference.

Any opinions on Daniel Defense's gas ports on these uppers?

can you remember specifically what and where you heard about this?

I'm not jumping your shit but I really do want to get to the bottom of this DD gas port deal. what I'm hearing is a couple of discussions that get taken out of context and repeated on down the line.

they may be or have been true in a specific instance but this is the type of stuff that can develop into an errornet "intelligence" dump - "Don't buy Daniel Defense, their gasports are drilled by the Devil!"

also, just remember a 10.5" barrel should have a different GP size than a 14.5 or 16. are we sure we're comparing apples here?