I probably spend more time than I should fooling around with ballistics calculators on the Internet.
When I’m looking to get a dope card for a new handload or a wildcat I’m working on, I tend to use this one at Handloads.com. I like the fact that I can put in any B.C. I want, add environmental conditions (I live at nearly 5,000 feet in elevation, so it does make a difference) and calculate my drop and drift out to 1,000 yards.
Winchester also has a good free calculator, which they’ve just updated to include a bunch of new categories like shotgun slugs and rimfire rounds. With Winchester’s calculator you can select from a number of pre-set factory loads and shoot them against each other. It is an illuminating exercise (or, as my boss would put it, “huge time suck”) to be able to compare a match .308 round, a .204 Ruger and the 25 WSSM in a head-to-head-to-head race.
(As it turns out, the .204 shoots flatter than the .308, but has much greater wind drift. The 25 WSSM is the best of both worlds–it shoots as flat as the .204 and bucks the wind as well as the .308. And yet, we all have .308s, a good number of us have .204s, and nobody owns a 25 WSSM. Go figure.)
The limitation of the Winchester site is that you can only shoot out to 500 yards (c’mon guys) and you can’t input your own data to reflect the real-world velocities at particular cartridges might develop in your rifle. But it’s a valuable tool, nonetheless.