Re: Lyman 9x19, 9x21 -- Why the difference?
2 grains of powder, 214fps and 4k cup is a big difference. The 9x21 is a more powerful round than the 9x19. When working with fast burning pistol powders 2 grains difference can blow up a gun or even worse. Coupled with a 2mm length difference you are talking a huge difference. 9.2 grains in the 9x19 could and probably would make pressures well in excess of the 33k cup of that load in the 9x21. The bullet sits a lot farther into the 9x19 case than in the 9x21 thus leaving less space for powder. This translates into substantial pressure increases on ignition. Plus the loads you have listed are the max loads. They are to be approached with caution to begin with. Please do not try to use the 9x21 load in the 9x19 case it could be hazardous to you health.
It's all fun and games, til someone shoots your bobber!