Dakor,
I made my 6mm-284 for the purpose on hunting rock chucks at ranges from 800 to 1200 yards.
I originally intended to use the 105 gr Hornady A-Max as it would perform much better at longer ranges as far as expansion and energy transfer.
Problem is that they let loose as far as accuracy at 3250 fps almost to the fps. At 3240 fps I was getting 1/2 moa groups at 400 yards and at the next test load up, 3265 fps, they grouped 1.5 moa. They just got worse from there.
I feel this is because I actually have more twist then needed for the 105 A-Max, a 1-9 would have been much better.
I just built a 6mm-06 for a customer using a 1-9 barrel and he is getting near 3600 fps with the 105 gr A-Max out fo a 28" barrel with groups in the 3's and 4's at 100 yards.
Anyway, I tried the 107 gr Sierra Mk and found it held extreme accuracy up to 3600 fps so I used that bullet.
On game this bullet is a relatively poor performer. On chucks past 800 yards, you better score a front end hit or the chuck will get down its den.
Still, if you connect in the front end it will instantly anchor a chuck out to at least 1055 yards which is my personal best one shot kill range.
On larger game such as coyotes its a different story. There is enough mass and resistance in the coyote to disrupt the bullet more and clean kills with this round and bullet combo are even more dramatic then on chucks at ranges out to 900 yards.
I would feel very comfortable shooting pronghorns on the open prairie out to the half mile mark. Deer I would limit to 600 yards like you say and to open country.
This 6mm is actually the reason I am building my 338 Kahn. I simply need more frontal area and energy for positive kills at ranges out to 2000 yards then the 6mm-284 will ever produce.
The 338 will drive the 300 gr Mk to 3100 to 3150 fps out of the 34" Lilja so it will certainly hit hard at 2000 yards. Trajectory and wind drift will even rival my 50 BMG at extreme range.
Still the 50 has a "slight" edge in terminal performance over the 338 Kahn
!
Good Shooting!!!
Kirby Allen(50)