initially, the weapons issued were of ww2 vintage such as lee–enfield rifles and sten submachine guns. in early 1972 the rifles were replaced with the standard issue l1a1 self-loading rifle (slr). other weaponry became available too: 9 mm browning pistols (browning 9mm), the sterling submachine guns (smg), the l4a4 light machine guns (bren lmg) and l7a2 general purpose machine gun (gpmg)s. small stocks of federal riot guns (frg) were kept and used to fire plastic bullets to knock down doors and other obstacles during search operations. a number of carl gustav (charlie g) 84 mm recoilless rifles were stocked but rarely deployed as the weapon was unsuited to most operations. (see boat sections below). slrs were replaced in 1988 by the sa80 and at the same time machine guns were superseded by the light support weapon. metal caltrops were used at vehicle check points to puncture tyres on cars trying to escape roadblocks.