Different powders have different burn times (as you already know) but theres more to just the shape of the powder.
For using a +P or a higher velocity round, you'll want a faster burning powder than normal.... IIRC the more spherical the shape, the faster, or more controlled it burns, but the composition of the powder is more important to how fast it will burn for.
If you trying to get some +P rounds, you can add a little more powder than usual... Although i do kind of recomend against it, i made some very hot stuff for a mark23...
With 'Unique' powder, (the maximum for 230 grain was 6.8 grains) i made some 7.5 grain loads... Very hot stuff! Generally guns can take quite a bit more than the "recomended" loads, but they will wear the gun out quicker (and we're talking by fractions here, not a lot...)
You can expriment with faster powders, but you'll need to talk to some gunshop reloader guys, for a 5 inch barrel, you may want to try some powder meant for 3.5 or 4" barrels... Say you need powder for a compact handgun... Just be sure to work up from smaller ammounts, so you dont go too overboard, because it will increase pressures.
Good luck!