The absurdity lies in why anyone tasked with managing the Imperium's heavily stretched resources would think an artificer's lifetime of work is worth one (1) dead heretic or alien, when that same artificer could instead craft enough regular-ass boltguns and bolter shells to kill thousands
of heretics or aliens.
The Imperium's workers are countless, but so are the Imperium's enemies.
Is one bullet ONLY thing he does? Maybe it takes lifetime to produce but not all that is active time so he can also do other bullets. After step x leave to holy liquid to soak in time. And maybe he can work on multiples at once.
This is the headcanon I've always accepted for the "takes a lifetime" in 40K
. 1 artificer can make hundreds if not thousands of the special bolts, but it takes them a lifetime to produce them. So a few times a decade the armory gets a new batch of them and then slowly issues them out a few at a time.
*edited for spelling