Whilst looking for a ballistic calculator i found a few that you may want to try. I have downloaded both to look at and to find out which one works the best. If you want to download your own copy of these programs then the first is : http://www.chairgun.com/ You get a free copy of the program but if you want to get rid of the splash screens that pop up when you start and finish the program you have the option to register your copy. Regisration costs £10.00 (see web-site for more info). They also have other free programs you can download too (ie Target template other calculators ect)
The other one is from : http://www.hawkeoptics.com/ This program works with most scopes and pellets.
I hope you find these programs usefull.