SAS Weapons - M16 & Variants
Whilst the SAS used the standard British rifle, the L1A1 SLR, a need for a lighter assault rifle with automatic fire capability was identified. The American-made M16A1 was soon adopted. It's 5.56x45mm round has neither the range or stopping power of the 7.62x51mm rounds fired by the SLR, but many more rounds could be carried by one trooper. For the SAS, who need to carry everything with them, this was a vital selling point. After some intial teething problems with the early models (AR-15) in Aden, the Regiment adopted the M16A1 which became the defacto assault rifle of the SAS for many decades.
Other units such as the SBS and specialist cadres within the Royal Marines and Parachute Regiment also use/used the M16. These days, the Regiment's M16s have mostly been replaced by the C8 carbine.
The M16 family of weapons includes several variants:
M16 A1/ A2
The ful-size M16A1, later replaced by the improved A2, was the most common variant in use by UKSF. The M16 has a magazine capacity of 20 or 30 rounds.
Basically, a standard M16 adapted to accept an underslung M203 grenade launcher. The 40mm high explosive grenades are a welcome boost in firepower and many SAS toopers elected to take the M203 with them on operations.
CAR-15 / Colt Commando
Developed for US Special Forces in Vietnam, these cut-down M16s trade range for compactness. Within the Regiment, these variants were more likely to be deployed in urban and covert scenarios rather than the open battlefield. On occasion, the SAS reportedly used Colt Commandos in Northern Ireland.