Don’t rule out the Bushnell DMR series. We have 4 of them in the family. 2 original ones & 2 DMR2s. Decent glass and pretty much bomb proof. A lot of scope for the money. Cameraland had some really good prices on them recently. Well below your budget.
Mine is still working after at least 10 years. Had to replace the wind impeller a couple of years ago but that's it. Gives you all the pertinent data you need for your ballistic program. Like Trigger Monkey said best to use lithium batteries in it.