Re: recoiless rifle
My MOS in the Corps was 0351, one of the listed weapons of that MOS was the 106 Recoilless Rifle. I was on one in Gitmo in 1972. I shot it once at 3 55 gallon barrels welded together floating out in the sea, probably about 500 yards out. I just shot over the top of them. The rifles we had mounted on early 1950s style jeeps, with a holddown slot in the windshield and bracket. We also had Mule vehicles, like early ATVs. The idea was for two rifle crews to work together on a tank from both sides. Shoot the aiming .50 sighting barrel with a tracer round, make aiming adjustments if necessary, then fire the 106 round. The crew immediately had to manuever the gun back on the Mule and get out fast, because if you didn't kill the tank, it had a returning round at you immediately. You telegraphed your position with muzzle flash, and dust kicked up.
To go against tanks was probably a suicide mission.
It was used some in Vietnam for direct fire support of your immediate area.