I mentioned in another thread about JUST getting a copy of Richard Lee's "Modern Reloading - Second Edition". I haven't even begun to read it!
In it, he discusses case capacity and how much it is reduced as rounds are loaded shorter in terms of both reduced case capacity and increased pressure (starting on page 96).
His example of a 1/16" (0.060") change in OAL makes a 14% change in case volume for a .45 ACP (it would be more in a 9mm, I think). There is a table that enumerates %change in pressure for 1% change in volume. For a powder like Titegroup, the %change is 2% for every 1% change in volume. That number is HUGE even with light loads.
Bottom line, be careful when you make large changes in OAL, especially on small cartridges.
I have mentioned elsewhere that I use 700-X for .45 ACP and I will admit that I get a LOT of soot and the cases have a black smudge on the outside. It's been that way for many years and I don't expect it to change. I just don't get too excited, one way or another. They go 'bang' and the bullet usually goes right where I was aiming (whether I was aiming correctly is another story) so I just keep making them.
"No matter how cynical you become, it's never enough to keep up." - Lily Tomlin