Sterling Submachine Gun - Design Details

Design Details

The Sterling submachine gun is constructed entirely of steel and plastic and has a shoulder stock which folds underneath the weapon. Although of conventional blowback design firing from an open bolt, there are some unusual features: for example, the bolt has helical grooves cut into the surface to remove dirt and fouling from the inside of the receiver to increase reliability. The Sterling uses a much-improved (over the Sten) 34-round curved double-column feed box magazine which is inserted into the left side of the receiver. The magazine follower, which pushes the cartridges into the feed port, is equipped with rollers to reduce friction and the firing pin is designed so that it does not line up with the primer in the cartridge until the cartridge has entered the chamber.

The suppressed version of the Sterling (L34A1/Mk.5) was developed for covert operations. This version uses a ported barrel surrounded by a cylinder with expansion chambers to reduce the velocity of the bullet to prevent it from breaking the sound barrier and causing a sonic boom, along with decreasing muzzle blast and flash. This is so effective that the only sounds during firing are from the bolt reciprocating and the barely-audible explosive discharge. The Australian and New Zealand SAS regiments used the suppressed version of the Sterling during the Vietnam War. It is notable for having been used by both Argentinian and British Special Forces during the Falklands War. It was also the weapon used by Libyan agents to kill WPC Yvonne Fletcher outside the Libyan Embassy in London which sparked the 1984 siege of the building.

The Sterling has a reputation for excellent reliability under adverse conditions and, even though it fires from an open bolt, good accuracy. While it has been reported that the weapon poses no problems for left-handed users to operate, it is not recommended without the wearing of ballistic eye protection. The path of the ejected cartridge cases is slightly down and backward, so mild burns can occasionally be incurred by left-handed shooters.

A bayonet of a similar design as that for the L1A1 SLR was produced and issued in British Army service, but was rarely employed except for ceremonial duties. Both bayonets were derived from the version issued with the Rifle No. 5 Mk I "Jungle Carbine", the main difference being a smaller ring on the SLR bayonet to fit the rifle's muzzle. When mounted, the Sterling bayonet was offset to the left of the weapon's vertical line which gave a more natural balance when used for bayonet-fighting.

For a right-handed shooter, the correct position for the left hand while firing is on the ventilated barrel-casing but not on the magazine, as the pressure from holding the magazine can increase the risk of stoppages, and a loose magazine can lead to dropping the weapon. The barrel-casing hold provides greater control of the weapon, so the right-hand can intermittently be used for other tasks. A semi-circular protrusion on the right hand side of the weapon, approximately two inches from the muzzle, serves to prevent the supporting hand from moving too far forward and over the muzzle.

The primary user complaint with the Sterling series is that there are projections in all directions, and carrying it on a sling frequently results in the weapon catching on clothing, load-bearing equipment, foliage, and doorways/hatches, as well as annoying (sometimes painful) poking of the user.