WW1 British soldiers show a captured German 13.2 mm Mauser 1918 T-Gewehr. World's first anti-tank rifle and the only anti-tank rifle to see service in World War I. The basis for those long barreled WW2 ones.
Back in the 70s a guy shot one at a collectors guild shoot at the Campbell town range Tasmania It had the bipod and each shot moved him back a few inches at a time from memory he fired 3 shots