"The 40mm Bofors, a semi-auto clip-fed Sharps rifle. With gain-twist rifling, no less
I realize there are variations, but the ones we had were full auto. I am pretty sure I remember the rate of fire was 240 RPM; 120 for each gun. The Duster had two modes of fire. One was manual (I can't remember if that is what they called it), and "power mode". In manual, you fired using ring type sights and the "trigger" was a foot pedal. The gun was traversed and elevated using hand cranks. The gunner had the elevation crank and the lead setter (on the other side of the gun) had the traverse crank. Sighting was done using the ring and also a rear apeture. In reality, you watched your tracer stream and walked the rounds into the target. In power mode, a console tilted up and you had a duel grips with a trigger button on them. The grips provided both elevation and traverse. The sight was optical; it had a glass plate that was very similar to a red dot optical sight that many of us use today on sporting arms. In power mode the lead setter ran what they called a computer, which was simply a mechanical device that moved your sight. The "computer" was set for direction of travel, and angle. Against ground targets the lead setter wasn't nessessary; you used your sights and walked the tracer into the target. In addition to the gunner and lead setter you had two cannoneers who loaded the guns. The ammo came in clips that I believe were four round clips. The rounds were dropped into the top of the automatic loaders. If you hoped to maintain any kind of continuous rate of fire you had to have other people humping ammo for the cannoneers since they were also in the tub. There were brackets on each side of the tub at the rear that held two clips a piece. Without assistance in humping ammo, you could fire maybe four clips from each gun with the ammo that was readily available. There was also two machine gun mounts; one at the rear of the tub and one in front of the lead setter position. We used an M60. The gun had tremendous recoil. The ammo came in cans that I believe held four clips. The ammo cans were used to chaulk the tracks on the range to prevent the whole vehicle from rolling backward under recoil.
At Camp Perry we fired the guns out over Lake Erie. We fired at aeriel targets which were radio controlled planes that were called ARCATS. They were about 10 feet long and were launched from a rail that was on a trailer. The ARCATS trailed a banner that you were supposed to fire at, but of course we fired at the ARCAT itself. I also fired at ground targets at Ft. Bliss Tx and Camp Grayling MI. We fired at regular civilian cars once and if you got on target on full auto, the car would roll through the desert until you quit firing.
The guns were bore sighted using a plug in the end of the barrel that had two wires forming a cross hair. A mirror thing was inserted into the breech end of the gun. You lined up the cross hair on a target that was at least 1200 yards away and then regulated your sights to coincide with the crosshair.
