по СQBR и MK18 вроде толково написано
"Both the MK18 and M4 CQBR come from NSWC-Crane, the NSNs for both items list Naval Sea Systems (the higher command for NSWC-Crane) as the manufacturer of the MK18 Mod0, however, the two items are listed under different NSNs. NSN 1005-01-527-2288 is the "us navy MK 18 MOD 0 carbine with 10in barrel" while NSN 1005-01-498-1913 is "navy issue M4A1 CQBR upper receiver with 10 inch barrel." Weapons in use by SOF were originally issued as M4A1s with 14.5" barrels. The CQBR is an accessory / additional upper receiver group utilizing a 10.3" barrel - originally cut down by Crane from 14.5" barrels, and later sourced from Colt. *ALL* SOF weapons, not just NSW, come from NSWC-Crane. They are the oversight for programs like the SCAR program and the SOPMOD program. NSWC-Crane does not mean Navy SEAL specific. Both the MK12 and MK18 were originally inteded and developed as accessory upper receiver groups for the issue M4A1. Both ended up evolving to complete weapon systems. The MK18 was originally envisioned as the MK18 CQBR - but when it evolved into its own weapon system with its own basis of issue, the MK18 component and CQBR (Close Quarters Battle Receiver) component were de-coupled. The MK18 weapon system became the MK18 Mod 0 Close Quarters Battle Rifle (unfortunately - also shortened to "CQBR") while the M4 CQBR accessory upper receiver group became a different entity. I don"t have exact dates on this divergence, but pretty much everything I"ve seen indicates that this occured during development, before either were really issue items, other than field testing, just like the development of the MK12 from a Special Purpose Receiver to Special Purpose Rifle. In other words, SOF, whether Navy SEALs or not, never used the MK18 Mod 0. They have always used a CQBR. The MK18 Mod 0 and M4A1 CQBR use a common upper receiver group - however, current M4 CQBRs are having the DD RIS II installed before being issued, since it is the SOPMOD Block 2 issue rail system."
About the MK 18 and the M4CQBR, there are differences betweem them: "Those weapons using the RIS II are CQBRs. The MK18 Mod 0 and M4A1 CQBR are two completely different things. An M4A1 CQBR is a 10.3" upper receiver group provided either in addition to or as a substitution for a 14.5" M4A1 upper receiver as issued by MTOE to SOF. The MK18 Mod 0 is a complete weapon system that can be ordered as such by conventional units with a need for them, usually to replace MP5s, but not always. This includes VBSS units and EOD units (un-verified). The MK18 Mod 0 was developed around the same time that the Mk 12 SPR was developed - both originally intended as replacement receiver assemblies for the M4A1 Carbine in use by SOF. Both eventually evolved into complete weapon systems, built by Crane and (usually) completed by a re-conditioned M16A1 lower receiver. For a short while when the MK18 Mod 0 was maturing into a complete weapon system - it bore a superficial resemblance to the M4A1 CQBR in use by SOF - using the VBL II gun light and ECOS-N (Aimpoint CompM2 in Wilcox mount) and KAC M4 RIS (as opposed to RAS). In many ways, at least in terms of parts, the MK18 Mod 0 is an M4A1 CQBR upper receiver group mated to a re-conditioned M16A1 lower and issued whole, rather than as a conversion kit for an operators existing M4A1. This is why you frequently see RIS II equipped CQBRs with CAR style stocks - the "host" M4A1 is an earlier lower that pre-dates the M4 style stock. On the other hand, the MK18 Mod 0 is almost always seen with SOPMOD stocks or less frequently with M4 style stocks - current spare parts. This is why the "Mod 1" nomenclature bothers me, because you"re compounding the mis-use of nomenclature. The CQBRs used by SOF aren"t MK18s to begin with. Therefore, there cannot be a "Mod 1" variant of it. On the other hand - for the most part, MK18s are still being issued in a "Mod 0" configuration and are still in the system as a viable, and complete weapon system. There"s evidence that many are being reset with 14.5" barrels however. Circumstantial evidence suggests these might simply be falling under the umbrella now of "M4A1," at least functionally, but they"re not the same thing as M4A1s, either. If nothing - then they should be MK18 Mod 1s, because they do not seem to properly match M4A1 specs, since USGI M4A1s all now use the RO921HB barrel profile, not the RO920 barrel profile like these 14.5" barreled MK18s."
