I've been doing some more analysis on my failed H268s. I've been under the impression that my nozzles were the weak link. I've since determined that primary cause of failure is most likely grain inhibitor failure leading to over pressurization of the casing.

The number one reason for utilization of Bates grains in earlier testing was for a flat thrust curve to maximize weight to thrust. By switching to a more flexible propellant mixture I can case bond the propellant to the outer casing.

The new mixture is 65/17/18 of potassium nitrate, sucrose, corn syrup. The method of preparation leads to some small amounts of water in the mixture from the corn syrup which is counteracted a little by being slightly oxidizer rich. The result is a slower burn which is more suited for lighter HPRs, but at the same time flexible owing to the corn syrup's liquid nature at room temperature, thus allowing for case bonding.

I successfully tested several low G high F motors with the new fuel.