as far as I know, noboody was allowed to purchase their firearms after WWI. in a couple extreme cases, some soldiers were awarded their rifles but that was only for MOH winners like Alvin York and the like.
during the civil war, the military was still very much disorganized and the war dept was getting ready to enter a very long and arduous arms race, muskets were just outdated and they needed a way to fund trapdoors and lever actions. by the end of WWI, everyone was using bolt actions and no one rifle seemed superior to what we had so there was no real urgency to sell what we had in order to fund better stuff.
the end of WWII and the economic struggles that followed prompted the huge amount of military surplus arms to flood the civilian market,
I'm still hoping that one day uncle sam will notice he's 17 trillion in debt and will start selling those M9s, M11s, M500s and M16s to civilians in an effort to help create a bit of slack.
all guns lost in a tragic smelting accident.
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Bean counters told me I couldn't fire a man for being in a wheelchair, did it anyway. Ramps are expensive.-Cave Johnson.