first of all put all your weapons in the storage if you can but keep 1 weapon that is worth alot of cash when you sell it

after you put most of your weapons into storage put the the only weapon you have left into 1 of the slots

then equipped that weapon must not be a gun

now hold LT and then press RT and Y at the same time this duplicates the weapon pick them back up then carry on duplicating until you have filled your inventory then sell them then repeate the process if you have any problems with this messege me on xbox

GT SHAGAHOLLIC