Been working with a couple of ballistics calculators and have come across a question that doesn't seem to be easy to answer - "How far will it go?" A little more detailed question - if I fire a 308 (172gn, BC of .452, MV 2800) at a 15 degree angle, how far will it go? How would you go about answering this? I understand this is not a question you would typically need to answer to create a firing solution, but is is of interest to those of us in the Eastern US - you can't get more than 2000 yards or so w/o encountering a structure of some sort, and it adds to overall understanding. JBM has a max distance calculator (i.e. given some ballistic information, it returns maximum distance and the optimum angle), but I'm looking to set the angle and determine the distance. This question seems to be a variation/extension of the shooting uphill problem, so I may be missing something. If calculators can't give this info, why not? Does this situation push the mathematical models (i.e. problems with going from supersonic to subsonic, etc). Thanks for your help...

Calculators typically dont factor in whether or not a given projectile will be stable after it goes subsonic. Most will NOT be. How far will it go? Typically, farther than when it goes subsonic. However it wont be accurate or straight. So in short, my answer is it will go as far as when it goes transonic. This is the usefull life of its flight.

Ballistic calculators can't determine whether a bullet will be stable when it goes transonic unless it has information abouit what the spin rate rate is as it goes transsonic. The spin rate at the muzzle is easily calculated from the mzzle velocity and the barrel twist, but there is no published coefficient iv'e seen to determine the rate at which a given bullet loses itfs rate of spin with time or distance. I'd expect that rate wold be related to forward drag, but I don't know what the realtionship is. Do any of you know of a study of the downrange spin rate of specific bullets?