#firearms design

A friend of mine came to me a week ago with this peculiar idea of an alt history where the Soviets cloned the M16 instead of adopting the AK-74. She acknowledges the entire premise is silly but it's for fun so who cares. Basically, she was looking for input on what changes they'd make too it.

The Other SIG 320

Many of us will be familiar with the SIG Sauer P320 polymer framed, striker-fired pistol, recently adopted by the US military as the M17. What we may not have known, however, is that the P320 isn’t the only ‘320′ to have been developed by SIG. In the early 1970s SIG developed a futuristic looking new submachine gun - the MP320. 

The MP320 was apparently the last submachine gun developed by SIG Neuhausen as a successor to the utilitarian MP310. Dispensing with the folding magazine housing that characterised SIG’s line of submachine guns the new MP320 had a futuristic profile with svelte side-folding stock and a top-mounted charging piece which removed the need for a protruding charging handle and reduced snag points and with no large charging handle slot it also limited the ingress of dirt into the action. 

In terms of disassembly it appears that unlike the earlier MP310, the MP320 has a barrel bushing which unscrews and allows the action to be removed through the front of the weapon rather than the rear. It’s unclear if any of the upper receiver lifts out of the lower.

The rear peep sight is enclosed in a protective stamped housing while the low profile front sight is positioned just in front of the knurled barrel nut. The weapon appears to make extensive use of stamped, rather than machined, parts with the visible parts of the upper receiver appearing to be largely stamped.

SIG MP310 (source)

The weapon had a large rotating selector switch on the left side of the receiver, just above the pistol grip with positions for safe, semi, three-round burst and fully automatic. While the MP320 abandoned the classic SIG folding magazine feature it retained the same double stack, double feed magazine which had been used right back to the MKMS developed in the 1930s. The magazine relieve can be seen at the rear of the magazine housing.

It is unclear what the weapon’s rate of fire would have been although its predecessor, the MP310, had a high rate of fire of around 900-1,000 rounds per minute. It is also unclear if, like its predecessor, the MP320 uses a standard blowback action - but this seems likely.  

I came across it while reading the Vickers Guide SIG Sauer Vol.1 and this appears to be the only current source of information on this interesting submachine gun. The book notes that the gun never went into production and development was abandoned after only a handful of prototypes were produced.

Sources:

Vickers Guide: SIG Sauer, Vol.1, (source)

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John Browning’s 1895 Slide-Action Prototype

In the latest Armourer’s Bench video I examine another one of a kind John Browning prototype. Patented in 1895, this slide action rifle design was purchased by Winchester but never manufactured. Instead Winchester went with the iconic lever-action Model 1895.

The rifle has a single-stack integrated box magazine but with a pump sleeve rather than a lever. An action-bar connects the slide/pump to the front of the breechblock/bolt carrier on the right-hand side of the rifle. The slide handle itself is made of a U-shaped piece of metal which wraps around the rifle’s forend. The slide has been roughly cross hatched to improve grip. There is a channel cut into the furniture for the action arm’s attachment point to travel. The slide is attached to the arm by a pair of screws.

Winchester purchased the .30 calibre slide-action design but never produced it, it is believed that only Browning’s prototype was built to prove the concept. The prototype was part of Winchester’s collection and may now be found at the Cody Firearms Museum.

The Sterling Submachine Gun Magazine: The Best Magazine Ever Designed?

In the mid 1940s, George Patchett set out to design a submachine gun and magazine that would improve on the STEN gun's shortcomings. The result was arguably one of the best SMG magazines ever designed. Robust, reliable and easy to use - the Sterling magazine is definitely an improvement over the venerable STEN's magazine.

Winchester 1866 Prototype Musket

The mid-1860s found the Winchester Arms Company looking to improve the Henry Repeating Rifle. A series of design improvements by the company's chief engineer, Nelson King, led to one of Winchester's most important rifles - the Model 1866.

In this video we examine a prototype 'musket' with an experimental loading gate quite different from the one eventually seen on production models. The prototype is a really interesting example of iterative engineering.

In the mid 1940s, engineer George Patchett set out to design a submachine gun and magazine that would improve on the STEN gun's shortcomings. Below are diagrams showing the make up of the two guns’ magazines.

First we have the 32 round, double stack, single feed STEN magazine. The STEN’s magazine was derived directly from that of the Lanchester Machine Carbine, which was itself a clone of the MP28, II′s magazine designed by Hugo Schmeisser. While the magazine was effective, with a tight control on the rounds fed into the action, it was difficult to load and prone to jamming in adverse conditions.

STEN Magazine

While George Patchett’s experimental machine carbine had initially been designed to feed from the same MP28/Lanchester/STEN magazines by 1945 he had decided that in order to improve reliability a new magazine was needed.

Sterling Magazine (L1A2)

Patchett’s magazine evolved over several years but its basic features included a a unique follower made up of a pair of rollers, a circular spring, a curved body - to improve the feeding of 9x19mm cartridges and it was of course double stack, double feed - which enabled it to be loaded easier. It held 34 rounds, on paper at least, and was robustly made from sheet steel with reinforcing ribs. 

The design seen above is the British Army’s L1A2 magazine - which was a slight simplification of the magazine’s produced by the Sterling Armament Company. The L1A2 magazine used two pieces of sheet metal, rather than four, however, it retained Patchett’s roller follower which. The rollers, in theory at least, could provide a stable feed and prevent jams by rolling dirt and grit out of the day.

Sterling Magazine (Patchett’s Sterling-produced original design)

Note the subtly different shape of the magazine, with the wall of the magazine making up the insertion guide and an extended lip at the sides to help prevent drop damage.

STEN Gun Magazine Loaders

We continue our STEN gun series by looking at the various magazine loading tools developed to help load the STEN's difficult to load magazines. Everything you ever wanted to know about STEN mag fillers.

Samopal 81 Krása

The Sa 81 Krása (meaning ‘beauty’) was developed in the late 1970s by Jiří Čermák, a Czechoslovakian Army engineer and designer. The Czechoslovakian Army requested that the Brno Research and Development Institute of the General Mechanical Engineering Works develop the weapon for use by troops who didn’t require a full-length rifle, including officers, artillery, logistics and armoured vehicle troops. 

The resulting personal defence weapon was based around the standard issue 7.62x39mm rifle round. It was just 31.5cm or 12.4in with its side-folding stock folded. This was 17cm or 7.1in shorter than the Soviet AKS-74u. Unloaded the weapon weighed in at 2.1kg or 4.6lbs, which in turn is 1.4lbs lighter than its Soviet counterpart. The Sa 81 fed from a 20-round magazine (the one pictured with the gun above appears to be proprietary) and had a hinged top cover, a side-folding wire stock and a short, fat flash-hider. 

It had a magazine well which protruded from the receiver, esquing the AK-pattern rifle’s rock to lock system. Interestingly the magazine well and release are reminiscent of those seen on the M16. It had a safety selector with positions for single, safe and fully automatic. While not ambidextrous the selector was marked on both sides of the receiver. The charging handle was positioned on the left side of the weapon with a folding, spring-loaded dust cover covering the ejection port. The prototype’s furniture appears to be wooden and of a blocky profile.

The Sa 81′s interesting gas-piston and bolt assembly (source)

Historically, Czechoslovakia was not afraid to forge an independent path from Soviet small arms doctrine having adopted the vz. 58 rather than the AKM. So the development of a local carbine was not surprising. The most interesting element of the SA 81 was its bolt. In order to keep the weapon short Čermák opted for a bolt which moved up and down. Rounds were pulled from the magazine and lifted up to the breech as the bolt moved forwards again. The Sa 81 was driven by a gas-piston with the breech locked by locking wedges.

The weapon was ready for testing by the end of 1980 and was refined over two years with efforts to chamber it in the new Soviet 5.45x39mm round, as the Sa 83. By the mid-1980s, however, the project have been abandoned. 

Zbrojovka BRNO (ZB) donated a prototype, Sa 81-6955, to the Military History Institute in Prague in 1991. The Military History Institute (or Vojensky Historicky Ustav) has a short, but detailed, article which gives us the bulk of what we know about the weapon.

Sources:

Trial submachine gun Sa 81, Vojensky Historicky Ustav, (source)