Maybe it is better if you would have your own shop at your own res selling the gunpowder, then people can just go to your res and buy them It's better than delivering as most people dont need more than a few stacks of gunpowder.. And most are lazy to make a shop just for this purpose
ok everyone i now sell gunpowder at my res for 15r the price is 16 for 240r which is 15r each my res is 648 on smp1