So I'm looking to find a substitute powder to replace the FFFg powder I normally use for live firing my 1863 Springfield, just for ease of buying and saving my FFFg powder for reenacting. I found some Pyrodex FFg equivalent (FFg is the correct grain size for civil war musket charges) but I can't find any info on if I can safely shoot it out of my 1863 reproduction or how many grains is equal to actual FFg black powder.

My 1863 is a modern reproduction, but although the pyrodex says it's a FFg equivalent, I just want to hear from anyone else who may shoot pyrodex what they usually do when shooting.