You can't use guns you loot from wrecks/npcs (with the exception of codes) because then anyone could use pretty much any gun they felt like with the claim of "I looted it." It may not strictly make sense in RP for junkers, but it's the fairest way all round.
There are many ways within the scope of what's allowed under server rules to get better guns, a deal with the Rogues for Sammaels for instance. Having just checked the tech chart, there's a variety of guns you could get access to with a bit of diplomatic work.
