"Yep, and I got more ammunition now that the NCR keeps supplies flowing in. On the other hand I'm payin' them NCR taxes, so now you got to as well."
Johnson Nash mentions he will have more ammo for sale once the NCR takes over Primm, but the player will have to pay more to cover the taxes. Well the vanilla game does increase the prices but doesn't actually give him more ammo. This is not a "pure" bug fix, so it likely won't ever be included in YUP. That being said, you are more than welcome to include this in any sort of compilation mod. There may be other mods that already do this, but I couldn't find any. Works with an event handler script and only hard edits Johnson Nash's vendor container. May need patches if other mods also edit his vendor container, but it would be a simple drag n drop fix. Let me know of any conflicts and I can upload patches here
Instructions
Install as normal with mod manager. Check for conflicts in xEdit and make patches/adjust load order accordingly.
Johnson Nash Ammo Fix
Main file. Required.