I just bought the cheaper app of Bullet Flite, highly recommend. You'll need your muzzle velocity though and a good guesstimate of wind speed, but I'm finding it's working well with my educated guesses!
As for ranges - make one. Maybe see if somebody can lend you a range finder. I've been practicing at a "natural" range using clearings on hills, rocks etc as targets. Best practice available in my opinion . You might need to take a spotter with some binos with you though.
Good luck
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