At 300+ yards, you're going to use your spotting scope to read wind/mirage conditions and see the shot markers. Do not expect to see holes at that distance even with the most expensive offering. Ideally, someone is in the pits pulling and marking the target for you, or even better, the targets are electronic and just look over at your phone or tablet. A Kowa 82SV with the angled eyepiece is the gold standard of buy one cry once in terms of spotting scopes. A tripod works. but not well. Ideally, you don't want to break your position to look through the spotting scope.
View: https://imgur.com/1oqDPSK
^^This^^. Regardless of the price/quality of glass you buy, atmospheric conditions will make it impossible to clearly see objects (targets/bullet holes, etc.) beyond 300 yds. Of course, perfectly still and dry air will be the exception, but that just isn't going to be the VAST majority of conditions any of us will be shooting in. When you start shooting beyond 300 yds, you're going to need to learn to read wind/mirage. You don't focus on the plane of the target for that, but rather various distances shorter than the distance to the target to read wind conditions on the way
to the target. For that, you don't need the biggest scope (large optics gather more light, so if you intend to use the spotting scope in twilight conditions, go as big as you can afford), but you DO need
clear glass. Unfortunately, that usually means more cost. You may end up using your scope to read wind/mirage for yourself, or to partner with another shooter to make wind calls for them. As
@dw617 wrote, Kowa's (and large Kowa's) are the gold standard you tend to see in matches for these purposes (and reading/calling scores). Interestingly, it is also common to see smaller scopes for the wind calling activities that have really clear glass (scopes like the Vortex Razor 11-33x50). Recommend also paying attention to the previous advice around buy once cry once. I went the other way as a novice and ended up purchasing several scopes as each revealed its inadequacy. (Scopes like Nikon Prostaff 3 [garbage], Athlon Argos [decent, but "milky" image compared to better glass], Vortex Razor [plenty clear and bright for most uses out to 500yds, and wind calling well beyond that], Kowa [Yes, just yes for anything OTHER than portability]). The balance, however, is that what you need is advised by the maximum requirements of how you will use it.
For most uses, I can't recommend the little Vortex Razor highly enough, and for $600-800 retail, it is comparable to much more expensive scopes. Good luck to you, and have fun with your pursuit of mid to long range shooting!!