[Little Ray]

There are lot of mistakes: defuse for diffuse. The 124.5 mm might be either a 12.5 mm (.50 cal) or 14.7 mm (the heavy Soviet MG). I bet it was the .50 cal.

[robertpaulsen]

I bet the .50 cal.

A 124.5mm round (the M1A1/2 tank fires a 120mm round) is about 5" in diameter. If it could stop that bad boy, it could certainly stop an RPG.