Shellite mixed lyddite with dinitrophenol to produce a filling stable enough to survive impact and then fragment the shell after penetration. Trials began with an unsatisfactory fifty-fifty blend and moved through fifty-five-forty-five to the sixty-forty wartime pattern. Postwar work continued toward a seventy-thirty mixture and tested other ratios. The development process balanced casing strength, fuze action, fragmentation, and explosive behaviour. Maximum explosive power was only one part of a useful armour-piercing shell.
Notable Point · 18:05-23:45
Shellite trades some explosive power for stability
The Greenboy improvement combined a more stable filling with a stronger projectile and better fuze performance, rather than seeking the most energetic possible explosive.