If you don't bother buying special ammunition whenever you go about doing the 'silvery rounds', you're doing it wrong.
And by 'silvery rounds' I refer to when you got from merchant to merchant buying the items you want/need, wait 60-90 minutes, rinse 'n repeat.
Nope, I am doing it right. Remember Al Fabet - that guy that goes around core city selling useless junk? I am that guy, but in larger scale.
I am always cycle most of the shops in the game through Core city -> Foundry -> Rails crossing -> SGS -> Junkyard -> Camp Hather -> Core city.
And guess what, You don't get much of those bullets at all because they are not being sold or build sold 6 rounds at a time.
Turns out that 6 bullets x 5 cities(camp hather doesn't sell those) = 30 bullets, per round. Needless to say this is incredibly low amount.