loading for antique revolvers

[laurencen]

been reloading for several antique revolvers for some time and never had a issue, I fill the case if anything a slight compress black powder, today a friend asked why I fill the cavity and not 3/4 fill to save powder when target shooting, good question so why do we fill the case with black powder? if it was half filled I assume it would not be good but why?

seems a dumb question but my friend wants to know

 

[farshot]

Black powder when burns expands very quickly and aggressively, and when such a space exists, rather than forcing a bullet out of the barrel, the gas can act within the air space as a small pipe bomb, causing an extreme pressure spike that can destroy your gun and maybe harm anyone nearby.

 

[Brutus]

Black powder when burns expands very quickly and aggressively, and when such a space exists, rather than forcing a bullet out of the barrel, the gas can act within the air space as a small pipe bomb, causing an extreme pressure spike that can destroy your gun and maybe harm anyone nearby.

Bingo. If you really need a lighter load you do what the Ruger Old Army shooters do.
Fill the partial space that you would normally top up with the black powder and replace that partial space with something like cream of wheat.
No airspace.
Edit: some use corn meal some just use extra fibre or felt wads too.