Anything past 750 almost requires a spotter if you're shooting precision. You're either mag'd up to see/hit a portion of the plate or backed out to just hit the plate. The former, you'll be lucky to see vapor trail, the latter, you can see but won't be precise on plate
For larger calibers, I actually find the 1k to a mile realm to be the easier to self-spot because of the time the bullet is in flight - it gives you the time to recover from recoil and get set for seeing the impact/miss. Obviously if the target is in front of foliage and/or the ground is wet, it gets tougher as you go out farther.
Inside 1k, even though it's tougher to get back on target quickly enough, the bullet energy is still enough that spotting has never been an issue with decent weight bullets - as long as your recoil management skills are up to par.
Outside a mile, it starts to get difficult to spot both hits and misses - even with a spotter. A couple weeks ago, I was out in the hills, and we had a target set at 1900. I was shooting my 300 PRC, my shooting buddy was shooting a 408 Cheytac. In my 300 PRC, I was shooting Berger 230s. The 408 was shooting 390 Cutting Edge solids. Which was easier to spot for? You'd be surprised.
With the Bergers, when they impact, they basically disintegrate. You see the black spot on the target through the spotting scope fairly easily, but you also see fragments of the bullet causing splash at the base of the target as well - very easy to know you got a hit. With the solids, they didn't really move the target much more (the target is heavy) and they don't explode or leave as much of a mark on the target. We also found that they would ricochet off the target (again, with minimal mark) and impact the ground in front of the target, causing me to call a low miss - we found several nearly intact bullets in the dirt. I'd experienced this with the Bergers before, but only rarely. It was happening with essentially every hit with the solids. In short, it was easier to spot the jacketed 230gr Bergers vs. the much heavier solids.