...the velocity retention (i.e., resistance to air drag) of various pellets - usually called "Ballistic Coefficient" - and tablulated the result. Of course the likelihood is that the pellet YOU want is either not on the list - or there but under some other badge, but such is life.
Here's the best one I know of:
http://www.computer4me.com/airgunjournal/pellet.cfm
Then - online calculators are available to predict velocity at any point downrange, given MV and BC.
http://69.6.222.74/airgunjournal/calc_fpes.cfm?
Alternatively, given MV, BC, and a predetermined velocity/energy, some will predict the range where retained V drops to the predetermined number.
http://69.6.222.74/airgunjournal/calc_range.cfm?
I've even made an attempt (which seems to match actual field results pretty well - bird and beast) to relate velocity, pellet weight, and caliber to wound penetration depth...
http://69.6.222.74/airgunjournal/calc_wchannel.cfm?
Should serve as a rough guide, anyway.
Steve