Welcome to the forum. In my opinion 40 cal is not good for hunting.Its kind of like just sticking needles in the game. The darts are so small and light in weight. Squirrels and crows are especially hardy and not easy to take down with 40 cal .If you have strong lungs a 6 foot 40 cal and heavier darts it may be possible with a extremely well placed shot. You can make heavier darts by buying wire from a hobby store to replace the existing shafts with a longer section of steel. 7 or 8 inches. Creating a broad head or finding a commercial one for the shaft. If your dead set on blowgun hunting consider a Large bore model..62 CAL.