It was cool and powerful, and I wanted to keep using it for a while, but my.50 disappeared in a flash. Do any enemies drop.50 bullets? I want to kill to get bullets. It always feels bad to spend money (yes, but it's weird that.50 bullets are similar to other bullets).
I've found in all my time in Starfield that finding specific bullets is a bit hit and miss in combat. I get exactly why you don't want to buy bullets (they are shockingly expensive in bulk), but you may have to do that for now until a modder creates a Fabricator that generates bullets at an outpost (which would be soooo useful).
I found a lot of that in the quest for the LIST call of help, repairing four sateliites and then battling the pirates in the starbase. Hope that helps, I wanted to loot much more but running out of space on my ship and helpers.
I just keep several favorite guns on my ship until I have plenty of ammo to carry what I want. It takes a bit, but if you pick up all ammo all the time, you'll get there. I started playing around with a magpulse and I had over 17k rounds because I DO NOT pass up on ammo. It weighs nothing so I can play with any new gun I get and if I like it I just note the ammo it uses and stock up at every opportunity =)