shoooter72,
Take it as far as it will allow. See how various bullets and loads behave and group on out there. You'll never know till you try and the practice will make you a better rifleman.
I have access to a little over 1800yds and I have shot to 1600yds, last summer. I was trying for the mile shot before deer season, but never made it. I did really good at 1500yds (10" group) with my 6.5-284Norma and 140gn A-Max's. I'm using ELD-M's in both my .300WinMag and 6.5-284Norma this year so I'm optomistic. The 1600yd effort was quiet humbling. The wind tore me up!
There's no way I ever figured I could shoot that far and that good. You gotta try! There's a 18yr old guy on this forum (under ELR) that built his own rifle (.300WinMag) and was shooting out to 2000yds w/215gn Bergers SUCCESSFULLY! That, I guess, is what motivated me to try it.
My shooting buddy uses the .308Win and for the longest time (before we started shooting together) had a nice (protected from wind) 700yd range. I tell you he was pinpoint from 0-700yds. I talked him in to moving out to the windy range with me for "real world" conditions (read as WIND!)
He had lots of doubts about the range of the .308 and dialing for wind. Throughout last summer though he got better and better with the wind and farther and farther. He did get one 6" group at 1400yds with his .308Win. Stock Savage rifle with a 10X SWFA (SuperSniper) and the military, 168gn sniper ammo? Not sure of nomenclature. Lots of guys told he and I that the .308Winchester would not shoot that far accurately. Not sure where his bullet is at in the "sonic" realm but it behaves nicely.
All this to say again, GO FOR IT! Keep us posted! JohnnyK.