Step 1: Materials
Materials list is pretty short:
All you need is your gun
A screwdriver (to get the head off)
Airsoft pellets or bbs
a strong straw
a mechanical pencil
a LOT of tape
perhaps a rubber band for the more auto-loady less dependable peice
Step 2: Remove Unnessasary Items
Just start unscrewing near the head or barrel until you can work it loose. Then if you want you can unscrew everything else to look at the guts and check if they work.
Step 3: Create Your New Barrel.
With this all you need to do is put a small hole in your straw which is smaller than your bbs. Then completely kill your pencil and have only the outer part and the "plunger" with the white part cut off. Then use your large amounts of tape to securely put the part on the outside over the straw and a little off to the side.
Optional: make yourself a little "bb door" from a tiny peice of another straw and tape that to the side of the barrel so it holds the bb in a tank thing better and you can aim anywhere.
Step 4: More Taping
Simply tape your straw onto place in your open nozzle of the compression tank so a bb can go back there against the "door" except that the loader is blocking the way.
Step 5: Testing, Adjusting, Testing, Adjusting More
Now to fire, put the bbs inside the open part of the mechanical pencil and put the "plunger" on top. Gently push down with the plunger until you feel a little give and the bb will have dropped into the compartment. Now if you want, check down the barrel and you should see the bb in place but held but the by indented straw. Now pump and shoot. If the bb doesn't come out, the mechanical pencil is held too toghtly on and open it up more. If the bb falls out it needs to be tighter. If the bb cant make if into the compartment the hole is too small and you're too far off.
Step 6: Shoot
Now pump and shoot.... pretty fast...