My reply should not be regarded as from experience with loading cartridges.
I am an avid muzzle loader shooter.
In a muzzle loader your load would be just fine.
I have never loaded, or even shot, a bp cartridge of any kind.
But, from what I know about guns, if your rifle is modern and well made the pressures should be well within tolerable/safety ranges.
Interesting question. I'll be following this thread.