Ok so! Here’s a write up for both the new and old edition 1500's as they are exactly the same. I'll be using an old edition. Much of this mod has been done before but this is my way and it's rather detailed for the noobs.
Materials Needed
1. Hot glue
2. Hacksaw/Dremel
3. Screwdriver
4.2 ft. K&S 9/16" brass
5. 2 ft. 1/2" sch 40 PVC
6. E-tape
7. Tubing cutter of some sort

Theres your gun, pretty ain't she?

Ok see those two orange pieces? They’re keeping you from opening the gun up. Rip, pry, burn etc those off without hurting the gun or pumpshaft. You can dispose of those pieces unless you need them for something else, but you won't need them anymore for this mod.

Ok so now that the orange pieces are off, unscrew all the screws and open your gun up. It should look something like that pictured above.

Now take the turret out, see the o-ring and screws? Don’t lose the o-ring or your screwed. Unscrew the screws to take the black part around the turret off. Set those aside somewhere and be careful not to lose them.

Ok there’s there turret, the barrels should come out pretty easily. Yank or pry them out at that line, if all else fails then go head and saw or something.

There’s the turret after yanking the barrels and air restrictors out. Now saw the remaining stubs off but don’t saw into the middle post. Make sure you cut around it.

There’s the completely barrel less turret.

Ok so for barrels, I decided to too nest some 9/16 inch brass in ½ sch 40 PVC. My barrels are 5 ½ inches long. Yours can be anywhere from 5-6.

To nest the brass, wrap both ends in e-tape till it fits snug in PVC. Then apply hot glue to both ends and shove it end and make sure it’s flush with the PVC and secure.

Now glue each barrel on one by one. Barrel alignment with the holes on the turret is crucial. If it’s not centered that barrel with fishtail darts. The darts are hit on one side instead of in all areas and it causes major range loss and fishtailing.