STEN Magazine Loaders

While the ongoing Coronavirus pandemic has prevented some archival research I had planned which would have informed much of the STEN series, our good friend Richard at the Vickers Machine Gun Collection and Research Association, has come to our aid and we’re able to cover some of the loading accessories developed for the Sten’s magazines.

As we know the Sten uses a 32-round double stack, single feed magazine which can trace its origins back through the Lanchester Machine Carbine to the Haenel MP28,II’s magazine designed by Hugo Schmeisser [patented in 1931].

Sten Magazine, inert 9x19mm rounds and MkII and MkIV magazine fillers

The nature of the single feed makes the magazine difficult to load by hand with the last few rounds very hard to insert. So a series of four marks of ‘magazine fillers’ were developed. These are described in the British Army’s official List of Changes in February 1943.

The MkI is described as consisting of “a lever mounted on a short case which conforms to the shape of the magazine. It is hand operated, the loading lever being given a rocking motion during filling. The MKI slipped over the top of a magazine with a rivetted spring tab which indexed into a notch in the front of the Sten mag.

A cutaway showing the MkII filler

The MkII is very similar but simplified by having the spring catch mounted on the rear instead of the side and engaged a “small rectangular slot on the magazine”. The rear of the spring is turned up slightly to allow the user to remove its from the magazine.

The MkIII, which is possibly the rarest of the fillers, is described as:

“hand operated but of different design from the MkI and MkII. It consists essentially of a spring loaded vertical plunger which is attached externally to a case, the latter to assemble on the magazine. There is no retaining catch. It comprises the following parts:

Case. Is a rectangular shaped steel pressing with a tube of rectangular section welded thereto. The latter, which houses the plunger and spring, has a hole trilled at the lower end to accommodate a pin which restricts the amount of movement of the plunger and acts as a stop for the compressing spring.

Plunger, loading. Is made of two laminated steel strips welded together the top part of which is set to form a handle. The body of the plunger is slotted to accommodate the compression spring. The top part is splayed to form a suitable contact with the cartridge.”

List of Changes, Feb. 1943
Sten accessories including a sling and a MkII magazine filler

The other more common filler is the MkIV. Which is a much simpler design with a loading lever mounted on top of a clip which is attached to the rear of the magazine body and retained by a spring similar to that of the MkII.

Rich has very kindly demonstrated the use of the two most common fillers – the MkII and the simpler MkIV. It takes Rich just under 2 minutes to load that magazine, but he was doing his best to show various angles and unlike a British soldier during the war he hasn’t regularly loaded magazines with one of these fillers either. Despite that the clip gives a good idea of how fast you could load a mag once you’re in the groove.

With the MkIV filler Rich was able to load the mag in about 1 minute 15 seconds, the stability of resting the base of the mag on the table helped with the MkIV’s simpler design.

Manual diagram showing both the MkII and MkVI

Also, as a follow on to our previous episode looking at the Sterling Submachine Gun’s magazine Rich has also demonstrated the loading of a Sterling mag to its 34 round capacity. No magazine filler needed with George Patchett’s double-stack, double feed magazine.

Massive thanks to Richard for taking the time to film the clips used in the video. please do go and check out Richard’s channel and www.vickersmg.org.uk.


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