The incident was part of a last ditch battle with the terrorist group in Syria, the Daily Star Sunday can reveal.
Members of the elite force have taken part in hand-to-hand combat against IS fighters who have vowed to fight to the death.
The bitter fighting battle place earlier this month as SAS troops from the regiment’s D Squadron working alongside Kurdish fighters forced the terrorists into a small pocket inside the town of Baghuz in Syria.
The SAS teams were moving around the outskirts of the Baghuz when they came under fire from an IS stronghold located inside a former bank.
One member of the SAS was slightly injured by a bullet ricocheting off the ground before a trooper on a specially adapted Army Landrover pummelled the building with a grenade machine gun (GMG).
The GMG, is a favourite weapon of the SAS and has a range of around 2000m and can fire 350 high explosives rounds a minute.
One source said: “After the SAS and Kurdish fighters came under attack, one SAS trooper opened fire with the grenade launcher to allow other members of the patrol to get into cover.“
The British troops got a fix on the ISIS stronghold almost immediately.
At least six grenades were fired directly into the building killing several of the fighters.
The soldier kept firing until half of the battle damaged building collapsed.
“When Kurdish troops returned a few days later they discovered at least 30 bodies inside the shattered building – all were IS fighters and most had died from shrapnel wounds from the grenades fired into the building.
“The automatic grenade launcher is a real force multiplier. It allows troops to lay down a massive amount of fire-power very quickly.”