Seekher2, nice to see another Canuck on the board.
Nice place you have there. Been in that country years ago. Yep, flat as a pancake. And then there is a tree!
I assume you are thinking about a plinking gun. At that range, trying to harvest any large game is well beyond my comfort zone.
So from a plinking perspective, you DON'T NEED a massive cartridge super boomer magnum. Fun though but not necessary.
What you do need is a bullet that will go sub sonic without loosing accuracy. The distance is far enough that ALL bullets presently produced launched from ANY cartridge and barrel will so subsonic. It's just a matter if its 1500yds or 2500yds. The only way to know if a bullet will stay stable is to launch it and see what happens.
I have launched 155gr Amax out of a 308 and gone to 1500yds. This bullet goes subsonic no problem at all. So, as some do, you can crank the rifle to the sky and launch bullets as far as you want to go. Some in the US shoot 308 to 3km's.
I prefer bullets of better ballistics and my favorite Canadian available and afforable are the 162gr Amax 7mm and 140gr SST 6.5. Out of the 7RM and 6.5-06, they are flying extremely well and at 1000m, very accurate. Assuming these bullet continues to do well after going subsonic, would be my top choices. BC for these bullets certainly exceed 0.6 (see my post elsewhere for data)
Don't get me wrong, I have monster 30 and 338 cannons as well. But availability of projectiles and cost of shooting these things is way up there.
Plus if the US restricts anymore reloading exports, you may have a rifle that you can't get components for ie 50BMG. Anybody you know stocking 240 or 300gr MK's?
If you like the high end tech stuff and want some high BC cannon fodder, contact Wildcat Bullets. They are in Sask I believe. I know he is a farmer too.
You should look at back issues of VHA as there was lots of info on guys trying to pop PD's at 2000 to 2500yds. They did not use the biggest cannons out there but their rigs were optimised for scope use and consistency.
Getting an adjustable scope mount for that range would be a big hurdle or a very expensive purchase.
At any rate, have fun and let us know how you make out.
PS, if interested, I am selling my 6.5-06. Will be very inexpensive for a 1/4MOA shooter. Contact at firstname.lastname@example.org