indoor ranges usually only require frangibles for rifles and high-powered pistol rounds (10mm or .357 magnum and up)
in general the only requirement is that the ammo have brass casings, as opposed to steel or aluminum. steel and aluminum cases are shitty, but a lot of people shoot them because theyre cheap. they dont feed well in a lot of guns, though.
however, the main reason ranges have such a requirement is because they recycle the thousands upon thousands of brass casings that end up on their floor every day. they sell them to companies that resell casings or do factory reloads, as well as to commodities companies who melt the brass down for resale. it's an easy way for ranges to make some extra income on the side, but it drives them up the fucking wall if some steel or aluminum casings get mixed in cause then they have to go and sort all of it. because of this, most ranges just prohibit people from shooting anything but brass. and believe me, range masters will jump up your fucking ass if they catch you shooting Wolf or Bear or any Eastern European milsurp ammo.
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