For a .50 caliber cannon you might be successful - if you mirror the features of a .50 rifle with which you are successfully using Pyrodex.
Pyrodex takes a bunch to get it to burn correctly - lots of resistance to push against. That's why it really fails with golf balls.
We generally try to eliminate too much resistance to keep pressure low (and safer). With a small bore (.50 cal) you will build up a bit of pressure as the products of combustion pile up waiting their turn to get out the end of the barrel. With big bores, 1" and up, you NEED windage (clearance all the way around the projectile) to limit pressure and keep the barrel in one piece.
For example, you will find that blanks sound right-much loud EVEN IF there's only powder with no packing nor projo. It's tougher to do with larger bores.