Zero experience with the 17 Rem Fireball itself, but lots of experience with the 17M4 wildcat that this cartidge commercialized after it being a wildcat only for almost 50 years.
Like with any firearm/cartridge, what you can expect is what you can muster with it at the time, especially with a pistol barrel and the fairly limited olptics available for them. This cartridge class is very capable. I've had custom M4 rifles that would easily shoot in the 2's or 3's, way good enough for long range varmints and predators. Shaving another .1" with your short tube probably depends on what moon phase you are in and how well you have aligned all your stars. Nothing wrong with shooting in the 6's at 100 with a pistol unless you spend a alot of time shooting zits off a gnats behind at 100 yards with it. IOW, .1" is kind of a moot point for any kind of hunting at any range with the barrel, and akin to trying to fix a wheel that really ain't broke IMO.
