system
Given the following post, respond as if you're commenting on Reddit:
human
[Fallout] Why is there so little variety in weaponry in the Commonwealth as opposed to the Mojave desert?

Even the slightest incursion into Boston can tell you that it was a bustling hub for the prewar military-industrial complex, like Cambridge Polymers, HalluciGen Inc., etc. but it seems like every other raider has to make their own guns literally from scratch?

As an example--there are only *two* choices of generic (non-unique) pistol in the Commonwealth: 10mm pistol or .44 magnum. Besides that you basically gotta make your own. In the Mojave you can find that and pistols chambered for 9mm, 45 caliber, .357 magnum, 12.7 mm, and a 5.56 mm.

It also appears that in Boston 9mm and 10mm SMGs are not available. Nor can you ever find an actual normal pump-action shotgun...
gpt
The Commonwealth was a hub of prewar activity sure, but the Mojave has Gun Runners making and selling new firearms. The NCR presence has something to do with it too, they're obviously using gear from prewar military stores and there isn't a comparable military outfit in the commonwealth.