As I address below, the silenced Sterling SMG still has great potential as a weapons for Special Forces Reconnaissance Teams and Battalion Scout Platoons. A modernised version in .45ACP which we will call The Stalker would prove even more useful.
The side-mounted magazine of the Sterling configuration allows the shooter to use a very low prone position. This is a very desirable feature of a weapon that may be fired from the extremely cramped conditions of an OP.
The .45 ACP round has better terminal capabilities than the 9 x 19mm, particularly at subsonic velocities. The .45ACP round is readily available and the standard loading is already subsonic when fired from most pistol-length barrels. This feature will make creating a suppressed weapon much simpler. If we assume a 4-5” barrel and a suppressor of around 10” length the suppressed .45 version of the Sterling is likely to be of similar length to an unsuppressed L2A3 9mm weapon.
Sterlings designed to fire from an open bolt show a good level of accuracy, even when fired fully automatic. Closed-bolt variants are reported to be even more accurate. The suppressed .45 has the potential to serve as a close-range sniping weapon. There may be situations where a threat can be eliminated by a single suppressed headshot. It would be prudent for the design to include adjustable sights and provision to mount an optic or night vision scope.
Although it has good terminal performance the .45 round has less recoil than an assault rifle round. Suppressors are noted for having a tendency to reduce felt recoil and muzzle climb. These features suggest that the Stalker will offer effective close-range firepower in the eventuality that a Scout unit is forced to engage in combat. The suppressed nature of the fire may allow threats to be eliminated without alerting nearby enemy units.
It would be useful if the SMG can accept .45 pistol magazines. Those from the Glock 21/30, Para Ordinance P14-45 LDAs or the SOCOM Mk.23 model 0. Fitting a shorter pistol magazine would make the weapon even more compact when used inside a cramped OP.
The Stalker may resemble the 4 Mk7 but would lack the foregrip, be fitted with a suppressor and have a longer sight base and scope rail.
Armament for OP teams.
OPs play a vital role in many scenarios. Effectively arming an OP team poses problems.
The unit has a lot of other equipment to carry, so can't afford the weight of heavy weapons.
The interior of an OP can be cramped, so compact weapons are preferable.
If discovered, the OP team will often be outnumbered, so will need considerable firepower.
The capability to quietly neutralize hostiles is also likely to be needed.
There is a solution to this apparently contradictory set of requirements. OP teams could be armed with weapons chambered in the 9x39mm round. Such weapons can be used for both sniping and automatic fire. The round is sub-sonic and easily suppressed but has twice the energy of a 9mm SMG round and more than three times the effective range. Unlike the 5.56x45mm round effectiveness is not reduced if fired from a short barreled weapon. Several suitable weapons already exist. The most compact of these is the Vichr/Vikhr
Given the often cramped conditions of an OP a bullpup configuration weapon would be useful if the ejection is designed so the gun can be fired from either shoulder without modification, allowing the best use of available cover.
To date, the only bullpup to have this was the experimental Steyr ACR. (Since the original publication of this article the FN F2000 and ST Kinetics SAR-21, both capable of ambidextrous firing have been introduced)
One of my thoughts was weapons such as the M4 could be given similar capability to the Russian 9x39mm weapons by fitting a 9mm barrel and mounting heavy 9mm bullets in .223 Rem cases.See the UPDATE below for more on this idea.
Failing the issue of suitable 9x39mm or 9x45mm weapons the OP team armament will probably be suppressed SMGs. Of the many available, the Sterling L34A3 has the advantage that it's horizontal magazine allows shooting from a very low prone position. 10 and 15 round magazines are available and suitable for use in cramped conditions. The American Gunsmith Institute claims the Sterling is most reliable SMG in the world. In one test the L34 silenced Sterling fired 60,000rds! It was then examined and the silencer and all other parts were found to be within required limits and quite capable of being fired further. A .45 ACP version of the L34 would be a very useful weapon, and since .45 ACP is already subsonic if fired from a 5 or shorter barrel the suppressor should be even more compact than that of the 9mm weapon. Compact machine pistols such as the Steyr TMP, Spectre, Jatimatic or Ingram/Cobray may also be suitable.
Another useful weapon for the OP team is a multishot grenade launcher. As well as laying down grenade fire to defend an OP it can also be used with canister rounds in a close range shotgun role. When on the move the Grenade launcher loaded with canister, CS, HEDP and WP rounds would provide much needed firepower in the event of the unit being ambushed. The grenade launcher can also mark targets for airstrike or air assault.
UPDATE The Whisper® range of rounds includes a subsonic .338 (8.58mm) round based on .221 Fireball brass that can be fired from M16 series weapons. The .300 Whisper® would be the prefered choice since it offers a flatter trajectory. In a supersonic loading the .300 Whisper® offers similar ballistics to the AK-47/AKM, so is quite suitable for close range defensive use and is accurate enough for sniping at under 200m. The bad news is that JD Jones, inventor of the Whisper® rounds has told me that the .300 Whisper® and larger calibre Whispers® will not feed relieably in some M16 magazines unless they are modified slightly. This rules them out as a general service round, but is not such a problem for small specialist units.
I've long been an advocate of arming long range units with a 7.62x39 M16 based weapon such as the SR-47. The utility of the .300 Whisper® does make one wonder if a heavier subsonic loading for the 7.62x39mm could be created.