This is a great write-up!
http://www.gunsandhunting.com/sweetheat.html

Interesting that, in his observations, it didn't require the regular bore cleaning the .17 Remington does.
I had a .17 Rem for a while, and that was pretty much the key- cleaning the bore with a bore brush about every ten rounds (patches alone wouldn't do).
If the article means anything, the 250 fps less velocity helps there.

The only .17 Mach IV (close to the .17 Fireball) I've messed with was in a 10" Bullberry Contender barrel. I've had it for over ten years, and done VERY little work with it, so I don't know if it needs the brush cleaning or not. If not, it may be an interesting round...although the screaming velocity of the .17 Rem was pretty much the whole point of it all.
It was fun to place an apple in front of a fence post, shoot it, see it turn to applesauce, and there not be a mark on the post from bullet or jacket.

My ".17 phase" was interesting and educational, but aggravating at times.

I have been hoping somebody would bring out a .20 caliber based on the .221 Fireball...this .17-.221 might be the next best thing....I also have a Model 77' Ruger in .22 Hornet that I have been seriously considering converting to .19 Calhoon...this may be a better way to go as I could keep my Hornet, which I have come to dearly love...