Overview[]
The MC-51SD is a possibly fake, British battle carbine, developed from the previously tested HK G3 conversion known as the MC-51. It was purportedly issued to special forces groups in the United Kingdom for trials to replace the dated, and at the time in-service, L34A1 suppressed submachine gun.
Naming[]
Although often named under a H&K designation such as "HK51SD," the weapon is not manufactured nor endorsed by Heckler & Koch. However, name fits the H&K system for naming firearms at the time, with the 5 standing for a compact firearm, and the 1 standing for the 7.62x51mm cartridge. Furthermore, the ending of the designation, "SD," is in reference to "Schalldämpfer," which sees usage in other integrally suppressed H&K firearms, such as the HK MP5SD series.
Development[]
By at least 1989, and potentially even earlier, the British Armed Forces expressed their intention to find a successor for the aging L34A1 submachine gun, which had reached almost forty years of service. In light of this, a British firearms company approached Bill Fleming, a well-known American arms designer, to develop several prototype models based on his short-barreled HK G3-platform conversions. Prior to undergoing trials with British special operations, the initial models, unofficially known as the "HK51 A3" or "Fleming Model 51" had been commercially available for purchase in the United States.
Cementing itself with Bill Fleming's series of designs, the United Kingdom had already made notable progress by introducing the MC-51, a short-barreled firearm based on the G3 platform, for limited testing with domestic special forces units. Although the MC-51 was considered as a potential replacement for the outdated L34A1, the version being evaluated lacked a crucial feature found in the L34A1, the integrated suppressor. An apparent solution to this missing feature emerged through the modification of the MC-51, wherein a sizable integrated suppressor was introduced, resembling the design and functionality of the MP5SD series.
Details regarding the procurement and design process of the MC-51SD are particularly elusive, as the obscure firearm lacks substantial evidence to substantiate its claims of authenticity, let alone its actual existence outside of aftermarket modifications in a present scene. If to be believed, than outfitting of the suppressor, would have been taken by original MC-51 designer, Bill Fleming, or another designer at FR Ordnance.
The evaluation of the MC-51SD would have ideally commenced shortly after the introduction of the standard MC-51 in 1989, with testing anticipated to continue until sometime in 1991. If such a firearm were indeed acquired, even for limited testing, the prevailing consensus during the evaluation of the MC-51 platform primarily revolved around the widespread notion that a compact firearm chambered for a full-sized rifle cartridge was ill-suited for most situations, given its compromised accuracy and cumbersome handling characteristics.
Authenticity[]
Whilst there is substantial evidence and thus numerous records pertaining to the base model from which the MC-51SD is derived, the MC-51, seeing testing with the Special Air Service and Special Boat Service, equivalent information about a firearm named "MC-51SD" seems to be considerably lacking when it comes to primary sources. Similarly, this situation applies to the more compact variant, the MC-51K, which is said to be a subcompact carbine resembling the style of the HK MP5K series of submachine guns. However, of course, some online sources still cite the firearm of being exclusively tested by only the Special Boat Service.
Despite the challenges regarding authenticity, Bill Fleming, the designer of the MC-51, had established a notable career specializing in conversion kits for the HK G3 platform, including various short-barreled options. These kits were commonly sold under the company name "Fleming Firearms" during the late 1980s and early 1990s. It is worth noting that Fleming Firearms has a documented history of selling subcompact models, which lends credibility to the existence of the MC-51K, at the very least. However, the same cannot be affirmed for any suppressed model, as legal restrictions typically prohibit the sale of such firearms with integral suppressors.
In recent times, the majority of images depicting not only the MC-51SD but the entire platform, encompassing the base MC-51 and the compact MC-51K, are predominantly airsoft replicas. This can be attributed to the prominent retailer Tokyo Marui, which sold plastic airsoft replicas during the late 1990s. Consequently, this phenomenon sparked a trend where customers converted their replicas into MC-51SD and MC-51K configurations, due to shared parts across replica HK MP5SD and HK MP5K variants, further adding to the proliferation of fake images online.
Variants[]
Gallery[]
 Weapons of the United Kingdom  After the Second World War |
|---|
| Infantry Weapons | ||
|---|---|---|
| Melee Weapons | Bayonet | [[]] |
| Survival Weapon | [[]] | |
| Sidearms | Pistol | L9A1 • L18A1 • L47A1 • L66A1 • L102A1 • L105A1 (A2) • L106A1 (A2) • L107A1 • L109A1 • L117A1 • L131A1 • L132A1 • L137A1 |
| Revolver | [[]] | |
| Machine Pistol | [[]] | |
| Close Quarters | Personal Defense Weapon | [[]] |
| Submachine Gun | L2A1 (A2 • A3 • A4) • L34A1 • L49A1 • L50A1 • L51A1 • L52A1 • L80A1 • L90A1 • L91A1 • L92A1 | |
| Shotgun (semi-automatic) | L128A1 | |
| Shotgun (manual-action) | L74A1 (A2) | |
| Primary Weapons | AR | L85A1 (A2 • A3) • L119A1 • (A2) • XL70 • XL73 • XL78 • XL85 • XL86 |
| AC | L22A1 (A2) • L101A1 (A2) • L119A1 (A2) | |
| BR | L1A1 | |
| BC | L100A1 (A2) | |
| Automatic Support Weapons | Light Support Weapon | L86A1 (A2) |
| Light Machine Gun | L4A1 (L4A2 • L4A3 • L4A4 • L4A5 • L4A6 • L4A7 • L4A8 • L4A9) • L108A1 • L110A1 (A2 • A3) • L130A1 | |
| General Purpose Machine Gun | L7A1 (A2) • L19A1 | |
| Heavy Machine Gun | L1A1 (A2) • L111A1 • L114A1 | |
| Long Range | Anti-Materiel Rifle | L121A1 • L135A1 |
| Bolt-Action Rifle | L8A1 (A2 • A3 • A4 • A5) • L39A1 • L42A1 • L96A1 (A2) • L115A1 (L115A2 • L115A3 • L115A4) • L118A1 | |
| Designated Marksman Rifle | L2A1 • L129A1 (w/ L17A1) | |
| Launchers | Grenade Launcher (Attachment) | L17A1 (A2) • L123A1 (A2 • A3) |
| Grenade Launcher (Standalone) | L14A1 | |
| Disposable Rocket Launcher | L2A1 • L72A9 | |
| Rocket Launcher | [[]] | |
| MANPADS | [[]] | |
| Non-Lethal Weapons | Pistol | [[]] |
| Underwater Weapons | Sidearm | [[]] |
| Rifle | [[]] | |
| Explosives | Anti-Personnel Mines | M18 Claymore |
| Anti-Tank Mines | L3A1 • L9A1 (A2 • A3 • A4 • A5 • A6 • A7 • A8) • Mine, Anti-Tank, L14A1 • L17A1 • L18A1 • L27A1 | |
| Practice Mines | L21A1 • L28A1 • L29A1 (A2) | |
| Anti-Personnel Grenades | L1A1 (A2 • A3) • L2A1 (A2) • L13A1 (A2) • L98A1 • L109A1 (A2) • L106A1 • L107A1 • L109A1 (A2) | |
| Smoke Grenades | L35A1 (A2) • L36A1 (A2) • L37A1 (A2) • L38A1 (A2) • L50A1 • L52A1 (A2) • L53A1 (A2) • L54A1 (A2) • L55A1 (A2 • A3) • L64A1 • L65A1 • L66A1 • L67A1 • L68A1 • L69A1 • L70A1 • L71A1 • L84A1 (A2 • A3) • L100A1 • L101A1 • L132A1 (A2) • L152A1 • L153A1 • L154A1 • L155A1 • L157A1 • L158A1 | |
| Practice Grenades | L3A1 (A2 • A3) • L4A1 (L4A2) • L16A1 (L16A2) • L28A1 • L56A1 • L73A1 (A2) • L83A1 (A2) • L108A1 (A2) • L110A1 • L111A1 • L115A1 | |
| Infantry Equipment | ||
|---|---|---|
| Clothing | Backpacks | [[]] |
| Body Armour | [[]] | |
| Bomb Suit | [[]] | |
| Elbow and knee pads | [[]] | |
| Signals & IFF | [[]] | |
| Suits | [[]] | |
| Vests & Webbing | [[]] | |
| Headwear | Communication | [[]] |
| Gas Masks & Rebreathers | [[]] | |
| Goggles | [[]] | |
| Helmets | [[]] | |
| Vehicle Headwear | [[]] | |
| Optics, Detection and Surveillance | Man-Portable Radar | [[]] |
| Mine Detectors | [[]] | |
| Night Vision Goggles | [[]] | |
| Periscopes | [[]] | |
| Rangefinders | [[]] | |
| Surveillance | [[]] | |
| Artillery | |
|---|---|
| Anti-Aircraft Guns | [[]] |
| Anti-Tank Guns | [[]] |
| Anti-Tank Guided Missile Launchers | [[]] |
| Anti-Tank Guided Missiles | [[]] |
| Grenade Machine Guns | L134A1 |
| Howitzers | [[]] |
| Mortars | 51mm L9A1 • 60mm M6(H) (-640 • -895) • 81mm L16A1 (A2) |
| Railroad Artillery | [[]] |
| Recoilless Guns | [[]] |
| Rocket Artillery | [[]] |
| Siege Artillery | [[]] |
| Land Vehicle Weapons | |
|---|---|
| Vehicle Machine Guns | BESA • Bren Gun • Browning M1919 • FN MAG • L4A4 • L8A1 (A2) • L37A1 (A2) • L43A1 • L94A1 |
| 30mm Tank Guns | L21A1 |
| 40mm Tank Guns | QF 2pdr HV • CTA40 |
| 75mm Tank Guns | QF 75mm • Vickers HV 75mm |
| 76.2mm Tank Guns | L5A1 • L23A1 • QF 17pdr • Vickers HV 77mm |
| 84mm Tank Guns | QF 20pdr |
| 94mm Tank Guns | QF 32pdr |
| 105mm Tank Guns | L7A1 (A3) |
| 120mm Tank Guns | EXP-28M1 • L1A1 (A2) • L11A1 (A2 • A3 • A4 • A5 • A6) • L30A1 • XL30 |
| Howitzers | 88mm 25pdr • 105mm L13A1 • 155mm L31A1 |
| ATGMs | BAe Swingfire |
| Aircraft Weapons & Munitions | |
|---|---|
| 7.62mm Machine Guns | L112A1 |
| 12.7mm Machine Guns | [[]] |
| 23mm Cannons | [[]] |
| 30mm Cannons | [[]] |
| 37mm Cannons | [[]] |
| Rocket Pods | [[]] |
| Rockets | [[]] |
| Air-to-Air Missiles | [[]] |
| Air-to-Ship Missiles | [[]] |
| Air-to-Surface Missiles | [[]] |
| Anti-Radiation Missiles | [[]] |
| Cruise Missiles | [[]] |
| Bombs | [[]] |
| Sources | ||
|---|---|---|
| Books | Online | Documents |
| • eliteukforces.info | ||