Re: 1000 yards with mosin nagant? anyone?
The 7.62x54R seems to like a 175-180gr bullet and IMR-4064. I'd jusdge its performance capability to be slightly more than the .308, and rather a bit less than the '06.
Using around 47.0gr (47.1 is the Sierra max) and the 175SMK, the cartridge performed well for me and my Son-in-Law in the Tokarev SVT-40 and Finn M-39 Military Arsenal/Sako-reworked Mosin-Nagant. Watch your pressures.
Our bores appeared well suited to .308 projectiles, but that's not always the case, and sometimes bullets sized for the .303 will work better.
The quickest way to find out is to try the .308's first, and if stellar accuracy can't be had at 100yd, try moving up to the .303's bullets. Download and watch pressures at first.
There's no cut and fast rule saying .308's won't shoot well in a .311/.312 bore, but properly sized bullets are always better. The rifle is the final judge.
For anything 500yd or under, using bullets heavier than 147-155 is not necessary.
Greg