If you want to discuss the logicality of some recipes, you're opening a big can of worms :-) (P.S. Can of worms requires steel pipe, animal organs and animal carapace).
The issue at hand here was that cartridges were "expensive"
And they're really not.
Beacons are easy, and all basic Tier 1 items which you should have tons by the time you get to the rifle. The "challenge" here is that it's probably going to be your first manufacturer if you're going to automate this.
black powder is easy to make.
And making the nobelisk, while again requiring a manufacturer if you want to automate, is not that expensive, the only "issue" at this point is finding a balance between making steel beams for the Mk3 belts and Steel pipe for rotors, stators and nobelisk.
As to the logic of the cartridge... maybe... It's a pre-loaded (nobelisk) single-use, single-shot barrel (=steel pipe) in a easy form factor. That's why you get 4 shots in a cartridge out of 4 pipes?
Where does the cartridge come from? Maybe it should really also need some plastic, and springs, and some paint , and lead for bullets... (I mean, if you wanted realism... :-)).
I'm going to guess the devs wanted "something" to put the manufacturers to use before you venture out to go make computers which needs a bunch of extra exploring and setup.