More powder = Bigger Fireball. So .44Mag wins. And even better is .460S&W and .500S&W.
Also try lighter bullets so they exit sooner and let more of the flames exit.
Also try 2400 powder. I've had great fireballs from that as well. Especially when using heavier bullets where the H110 was dying down before the bullet let it out.
The guns with the shorter barrels also help with all this. As does having one with a cylinder gap that is on the wider side of the allowable range.
And for the most effect take them out on the dullest days with the most overcast. Stuff that you can barely see in sunlight takes on epic proportions in the near dark....
The only "issue", if you can call it that, is that the best fireballs come from max or near max pressure loads. But perhaps try playing with this factor to see if downloading within the range allowed to produce lower pressure might slow down the burn and leave more flame for the open air.
I know that I've shot some .38Spl factory ammo that had a HUGE fireball. And it wasn't even that strong a load. So there's a few different factors that are worth playing with if you're an enthusiastic flame hound.
Needless to say I'm one as well. I won't be happy until I've produced a flash load that goes off like a camera flash and blinds me for a few moments....
