Lore-friendlyish big guns mods?

Hey all I'm just trying out NV again for the first time ina while and I was looking around for some heavy weapons mods that aren't too lore-conflicting. There was a cool .50 cal HMG mod a few years back that seems to have vanished. I'm also having trouble narrowing down search results on the nexus. Hoping that someone here could point me in the right direction.