Robot tank run amok, its trainer trapped in cave on the Moon

Question

Another dim memory from my sci-fi reading binges in the 1980s... this one almost definitely in one of the big hardback collections full of late Golden Age short stories.

The story is told from the perspective of a robot (maybe cyborg?) tank that has stopped responding to control signals and is aggressively "defending" some portion of the Moon, to which it was previously assigned. Maybe a war had ended, or maybe it became confused about an exercise that it thought was real?

There was a person trapped in a cave trying to communicate with the tank. The tank mostly ignores him, so the main purpose of what he says is exposition for the reader. I think this person was an expert on this type of robot/cyborg sent to "talk it down", but the tank had attacked, and this guy was the only survivor. The expert was badly wounded -- I think he mentions his suit had to amputate his leg to seal a hole -- or maybe flood it with water which would freeze to seal the hole but mean that his leg had to be amputated later. He keeps trying to convince the tank to stand down, at one point saying that he knew it "back when it was just a two-wheeler an autocyber in boot camp" or something along that line. (Edit: I must have been reading too fast and/or distracted back then, since per the quote below I seem to have misread "motorcycle" for "autocyber"!)

One detail of the attack stands out -- the tank was low on ammunition, I think, so it used a kind of bomb with an electric/magnetic "catapult" (aka "magnapult") to hit the expert's transport. The tank was proud of itself for figuring out a way to hit it far out of the normal range by 1) using its own top speed to add velocity to the projectile, and 2) building up the catapult's energy past its normal operating range, which caused it pain but made the bomb go much further. It catches the transport by surprise, since they thought they were safely out of range of the armaments it had left.

The premise sounds a lot like a Keith Laumer "Bolo" story, but I'm fairly sure that it's not actually one of them. It had a somewhat grimmer feel to it. I could be wrong, though, since it's been 30 years.

Answer 1

"I Made You"

This is a short story by Walter M. Miller Jr. It has been published multiple times.

The only survivor of the tank’s assault is a man in a cave:

The land was silent, airless. Nothing moved, except the feeble thing that scratched in the cave. It was good that nothing moved. It hated sound and motion. It was in its nature to hate them. About the thing in the cave, it could do nothing until dawn. The thing muttered in the rocks

The person trapped in the cave mentions he knew the tank when it was young, in an attempt to make it stand down.

“I’m your friend. The war’s over. It’s been over for months . . . Earthmonths. Don’t you get it, Grumbler? ‘Grumbler’—we used to call you that back in your rookie days—before we taught you how to kill. Grumbler. Mobile autocyber fire control. Don’t you know your pappy, son?”

It hits a target out of range by building up the energy of its weapon, causing itself pain:

It analyzed the reports of the emissary ears, and calculated a precise position. The enemy runabout was 2.7 kilometers beyond the maximum range of the magnapultas creation had envisioned the maximum. But creation was imperfect, even inside.  

It loaded a canister onto the magnapult’s spindle. Contrary to the intentions of creation, it left the canister locked to the loader. This would cause pain. But it would prevent the canister from moving during the first few microseconds after the switch was closed, while the magnetic field was still building toward full strength. It would not release the canister until the field clutched it fiercely and with full effect, thus imparting slightly greater energy to the canister. This procedure it had invented for itself, thus transcending its programming.