The rule, long established, is that smokeless powder (not including Pyrodex etc.) is not to be used unless is in a properly designed cartridge with adequate priming and separate ignition charge if required. Just one of the problems you can run into with charge geometry is standing wave generation. Standing waves really have no limit as far as psi, and most instrumentation ends at 200,000 psi or so. I've known standing waves to blow up a Navy 76mm gun just because a flash suppressant charge was put in and changed the internal geometry of the charge very slightly.
Don't do it unless you have an advanced degree in engineering, have worked it all out, and have experience in that field, or you will probably blow the gun. Anyone with those qualifications won't do it anyway, they know what'll probably happen.
I also saw a 16" naval gun blown up because some engineers decided to shoot a blank charge with a hay wad. They used 40mm Bofors gun powder as the noisemaking charge. That hadn't been done before but it oughta work, right? Wrong! The 40mm powder didn't like that geometry and decided to detonate, which welded the breechblock into the threads, and it never could be opened again. The gun had just been refitted and drilled for pressure ports for testing, at a cost of about $5M of your money.
If you are bent on suicide, go stand in front of a train, it is less painful than having high-velocity metal fragments rip into your body.
