Drill into the coupling to get rid of the thread. Create a 9/16 inch diameter hole 3/8 inch into one coupling to get rid of the thread. This drilled section must fit securely over the smooth section of the pipe.
Next, drill a 25/64 inch diameter hole 3/4 inch into the pipe. Always use the cartridge you want to use as a gauge. When a cartridge is put into the pipe, the base of the jacket must be even with the end of the pipe. Thread the coupling tightly onto the pipe, drilled end first.
Drill a hole in the middle of the pipe plug just big enough for the nail to go through. The nail has to be centered in the plug. Push it through until it’s level with the squared-off end of the plug and round it off if needed with a file.
Curve the metal band into a “U” shape. Drill two holes in the flaps to fit the diameter of the wood screws you’re using. This will be utilized as a basic hammer to spring forward and hit the bullet, using the rubber bands to make tension. So, you might want to notch some little notches into the metal to stop the rubber bands from slipping.
Fashion a basic stock and handle from wood. The design is yours, but it needs to be around an inch thick after being drilled and at least two inches longer than the assembled length of the pipe you’re outfitting. Drill a 1.43 cm hole through the stock, around 1/2 cm from the top.
Push the pipe through this hole and attach the first of the two couplings to the front tip and screw the drilled plug into the back end of the pipe, the end nearest to the handle.