The mounting could engage both surface and air targets, but human crews supplied its training, elevation, and visual control. The demonstration makes the physical work audible and visible instead of reducing the system to a specification. Manual movement became more demanding against a nearby fast target, while smaller angular changes could cover greater distances at long range. The arrangement was nevertheless reliable, straightforward to maintain, and likely to remain available during repeated convoy missions far from extensive support. That tradeoff suited a class whose value came from many working escorts rather than exceptional performance by one ship.
Notable Point · 50:35-53:37
Operating the manual high-angle 4-inch mounting
A hands-on demonstration shows the effort required to train and elevate Diamantina's manually operated high-angle/low-angle 4-inch gun.