Since you asked, here is my take.
The 168 SMK is a great bullet for 600 yard work.
I will suggest you take a look at the 175 SMK if you want to play at 1000.
Work on your technique first and think about playing at 600 before you go to 1000. There is a lot of wind reading to the game and it doesn't get easier with distance. You can go through a whole bunch of 168s at 600 while you learn to stack them into the 10 ring on your way up to 1000.
Right now factory ammo is hard to find in general, but if you can find a box of FGMM in the 168 and or 175, you will get a good baseline performance and speed. Unless you are worried about close range penetration of some sort, always orient your load development towards accuracy and try not to chase velocity.