Again, no personal experience loading or shooting the .17 Squirrel but...
It is a short cartridge based on the .22 Hornet case, case length is just under 1.0" long, 20gr bullets can go up to 3,000ft/s or more. Case forming is a bit of a chore, I made a form die set for a guy and tried it out, seems like it was 3 steps plus FL. You have to trim a lot off the original case and several people have modified some mini chop saws from Harbor Frieght to use a quick brass choppers to make this easier. Loads run from 5-8grains of fast powder and the small capacity makes it VERY sensitive to load variations so you need a good measure or hand weigh for optimal accuracy. Supposed to be tons of fun once the brass forming is over with!
More information is available in "The Sensational Seventeens" (.17 CCM also) and in the magazine
Small Caliber News- Summer Edition 1998, Vol1, No.2, both available from the Woodchuck Den 330-897-0614
http://www.woodchuckden.com, but when I ordered one issue he sent and charged for the entire year which I did not ask for or expect. I think the magazine is under new management but don't know what that may have changed, I don't have a subscription only a few issues.
Also lots of info at
www.saubier.com, small caliber enthusiast forum, helpful folks.