If you don't have access to aluminum foil (which you can turn into aluminum powder using a ball mill) and rust (which you can make using any iron source with oxidizer like common household bleach), then I'm going to have to question the ease you'll have making a useful guncotton based propellant.
There was a book, "Jack Hinson's One Man War" which describes the exploits of a confederate sharpshooter who used a custom made 50 cal black powder rifle and iron sights to make long shots, out past 800 to 1000 yards if I recall correctly (I may in fact not recall correctly, it's been a while since I read the book).
If you really want to start making long range rifles in addition to your new subgun effort, you don't lose anything by going the black powder route first as a training exercise, at least as long as it's legal for you to do so.
Jimro
There was a book, "Jack Hinson's One Man War" which describes the exploits of a confederate sharpshooter who used a custom made 50 cal black powder rifle and iron sights to make long shots, out past 800 to 1000 yards if I recall correctly (I may in fact not recall correctly, it's been a while since I read the book).
If you really want to start making long range rifles in addition to your new subgun effort, you don't lose anything by going the black powder route first as a training exercise, at least as long as it's legal for you to do so.
Jimro