If he is using the flint system he has to use black powder to get consistent ignition.
If he is sing a cap lock system he can use artificial black, which is easier to source due to not being considered an explosive.
The ignition temperature of the artificial BP is higher than the real stuff an requires a good hot flash to fire it. Flint sparks will not normally do so.
What is artificial black ? MB .....not heard of that....there again i do not own any guns other than a air rifle.......this maybe dangerous ground MB ! if you feel the need not to reply ...that's fine and very understandable.....
artificial black powder is modern propellant designed to behave in a very similar way to black powder with the exception that it does not blow up but burn quickly instead , the common brand/type in use in the UK is pyrodex , it's used in the main because there are no storage and licencing restrictions imposed on shooters unlike real black powder which is quite highly regulated , it is freely available to buy to anyone , black powder is not!
Good shot MM!
Artificial black also has the advantage of being extremely forgiving. It is almost impossible to blow up a cartridge gun with the stuff. One simply can not get enough of it into the case to blow the gun.
Reloading rules for it are; put in a primer, fill up the case, seat a bullet on top, shoot.
But it does make a lot of smoke and you have to thoroughly clean the firearm immediately after use. It is very hydroscopic.