Hudson M21 gas blowback rifle has changed a great deal since the first announcement.

If one would look for most secretive airsoft gun releases then maybe Hudson M21 sniper rifle would get the position #2 right after Marui M14 AEG. To be honest there has been fair bit of skepticisms among veteran people about how or even if Hudson can release this rifle. The skeptics might have to re-evaluate their opinions as it seems Hudson is closing on the actual release of M21 gas blowback rifle and in the process they have finally revealed first details about the proposed mechanism. The appearance of the rifle has changed considerably in the process since we took the first photos on January 2004.

Now that Hudson has revealed details of the mechanism it is surprising how the rifle differs from the early predictions.

Background of M21 sniper weapon system
The M21 sniper weapon system is upgraded M14 with scope sight and was originally developed for combat use in Vietnam. Since it’s introduction in 1969 it has been replaced in US Army by M24, but the M21 is still in use throughout the US Army as seen in on-going conflicts in Iraq and Afghanistan.

Early M21. Images US Army.

ART I and ART II scopes for M21. Images US Army.

”The National Match M14 rifle and its scope makeup the M21 sniper weapon system. The M21 is accurized IAW United States Army Marksmanship Training Unit specifications and has the same basic design and operation as the standard M14 rifle (FM 23-8), except for specially selected and hand-fitted parts.”
-US Army Field Manual 23-10

Besides of the official US Army use Springfield Armory is also offering M21 Tactical variant that differs slightly from the US military M21 and which is advertised to be in use with ”spec-ops groups world-wide”.

“The M21 Tactical rifle is the ultimate in auto-loading accuracy. In active duty with elite spec-ops groups world-wide, the M21 is the ultimate tool for the law enforcement sharpshooter. Accurate, reliable and powerful, the M21 rifle remains the world class standard for sustained precision fire.”
–Springfield Armory describing their M21 Tactical rifle

The XM21 Sniper Rifle was developed jointly by the Army Weapons Command (Rock Island, IL), Combat Development Command (Ft. Benning, Ga), and the Limited Warfare Agency (Aberdeen, MD). The XM21 was an accurized M14 National Match (NM) semi-automatic rifle equipped with a Leatherwood 3X-9X Adjustable Ranging Telescope (ART). The Rock Island Arsenal converted 1,435 M14NM rifles to XM21 sniper rifles for initial fielding to Vietnam in 1969. The rifle was initially fielded with a hardwood stock, which was later replaced with a fiberglass stock. The XM21 was officially type classified M21 in 1975, though it had been informally called the M21 since December 1969. It was the primary Army sniper rifle of the Vietnam war and remained standard until officially replaced by the bolt-action M24 Sniper Weapon System beginning in 1988. However, despite the introduction of the M24 the semiautomatic M21 remains in US Army use to this day. The M21 uses U.S. match grade M118 NATO 7.62mm cartridges, in five-round or 20-round magazines. The ART telescope featured a variable magnification power of from 3X to 9X, for adjustable ranging between 300m and 900m. This adjustable ranging feature removed much of the guesswork from aiming at the target. The ART was ballistically matched with U.S. M118 NATO ammunition (1,800).

Modern day M21 of US Army. Seen here with ART II scope. Photo DoD.

Hudson M21 Gas Blowback Rifle

As speculated earlierly it has been now confirmed that Hudson M21 is using great deal of parts, as many as 70%, from the Hudson’s M14 model gun. In addition the first lot will have real McMillan stock that will further increase the external realism of this rifle.

Looking at the weapon design the mechanism and build of M14 rifle are not the easiest for gas blowback gun manufacturer. The bolt has operating slide and both bolt and piston are as one inside the receiver. In addition to the weight that the bolt and piston present there is a additional burden of recoil spring and the movement distance of blowback is reported to be 84mm. To power such heavy blowback part for so long distance lot’s of energy is naturally required.

Hudson M21 magazine and trigger assembly. Photo Gun Magazine

Hudson has overcome this significant obstacle by changing the whole idea of blowback mechanism. What Hudson has done was to design the power source to be fed by two routes. First route feeds gas from magazine for shooting BB and for blowback action gas is send separately from the backpart of the stock. This two-way type gas blowback is according to Gun Magazine similar to old Marushin UZI or Government mechanisms. What is interesting is that the blowback gas-route is not actually feeding gas, but CO2, air. It means that in practise the rifle is powered both by regular gas from the magazine and pressure regulated green gas from the stock. The law in Japan requires the regulator and it is unknown at this stage if the Hudson M21 can take green gas without the regulator. It is reported that because of lack of space inside the magazine Hudson invented this two-way gas system. The two-route feeding system should also allow smoother mechanism action.

Going with the current MilSim trend the big magazine of M21 contains gas for shooting BB and has BB capacity of only 20 BBs – same as the real gun.

The CO2/green gas tank is currently externally carried, but might be possibly located inside the stock in final version.

Mechanism details
When you cock the rifle by pulling the cocking handle first BB is moved into chamber and hammer raises up. There is a loading nozzle inside of the vault to lead the gas from the magazine into to the muzzle of the gun, but there is no piston which you can see usually in blowback airsoft guns.

Trigger mechanism is reported by Gun Magazine to be almost same as the real one, but with addition of few parts.

On left side of receiver, just in front of the operating rod, there is a pipe which purpose is to guide gas for blowback. There is cylinder (gas cylinder)under the barrel to accumulate this gas and a to keep out the operating rod to backside. When the trigger is pulled cocked hammer goes down and the connected knocker (trigger assembly part) pushes the valve into backside of magazine.