Try Paypal, very anti-gun, if you state "gun/firearm/AR-15/M16..." in payment note they will took your money and shut down your account. And try ebay, i tried to sell an AR handguard and forgot to mark it as Airsoft/model, ebay fined me about 5 dollar for that and prohibited me from selling for 2 months.
If corporations keep this up we dont need the govt to ban guns, these corporations can just pay unemployed people to do suicide house break-in mission and grab guns.
I actually shipped a gun part not long ago at UPS, I knew someone is gonna bitch if i mention guns, so i put it in a black sheet and shipped as hardware. Fuck their policy.