The topic has come up from time to time about using Pyrodex instead of 4f black powder for ejection charges. We have found the secret to using Pyrodex as a direct substitute for 4f black powder after conducing a series of ground tests and successfully flying rockets with various sized ejection charges all of them using 100% Pyrodex instead of black powder.

The Pyrodex to use is Hodgdon “P” or FFFG Equivalent for ejection charges in PVC pipes sealed on one end or phenolic tubes sealed on one end. The sealed end is usually a PVC fitting with a hole in the middle for the electrical wires to the e-match.

We used about 1.3 times the weight of 4F black powder for the weight of Pyrodex “P”. So if you used 1 gram of 4F black powder, use 1.3 grams of Pyrodex “P”. After putting the powder in the open end of the tube, we put a wadding material in the tube. We filled the rest of the open tube with wadding so that the powder stays at the base of the tube.

On the open end of the ejection charge tube, we would normally use masking tape to seal the tube when using black powder. For the Pyrodex, we used electrical tape to seal the tube. We put one piece across the open end of the tube with the ends of the tape going down the side of the tube. Then, we put another piece of electrical tape across the open end of the tube 90 degrees to the first piece with the ends going down the side of the tube. Looking at the end of the tube, it makes a cross pattern. Finally, we put a piece of electrical tape circumferentially around the tube at the end where we had put the electrical tape. This piece of tape goes over the ends of the first two pieces of tape. That’s it.