I thought the nitrocellulose-based powder used in firearms cartridges burns too slowly to be particularly suitable for use in bomb-making.
Wouldn’t he have been beter off purchasing black powder if he wanted to build a ‘gun-powder’-based bomb?
If you highly constrain the burning, you can get a pipebomb that is not very effective.
There are other things that you can do that I would rather not discuss, if you use the gunpowder as a base.