First off get at least 12 prayer potions and melee gear and use the training teleport. Then walk northeast to the Elf Warriors. You will want to pray protect from range and kill them until you get a crystal bow drop.
[You must be registered and logged in to see this image.]Then equip range gear, your crystal bow, and 1 bolt rack.
[You must be registered and logged in to see this image.]Then you will want to go back to the Elf Warriors with your range gear and and your prayer potions. Attack the Elves and once your bow reaches 9/10 the bow will start dropping bolt racks. It is possible to get bolt racks on other monsters but it would be smart to use them on the elves because you can get more crystal bows therefore granting you more bolt racks!
[You must be registered and logged in to see this image.] GO! GET YOUR BOLT RACKS NOW!
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