Hornady lists a 175 at a max of 2650.
I have been shooting a 7x64 for about 5 years now. I use 280 data and run it up about 100 fps slower than a 280 would run the same bullet.
The lastest Hornady manual shows pretty much the same trend. However, the 7x64 will use more of the same powder with the same bullet to run 100 fps slower.
140 NBT runs a shade under 3000 with RE-19.
140 TTSX runs 2958 with RE-19.
160 AB runs 2777 with IMR-4831.
These were worked up in my gun. I am also at 4500', so my velocities will most likely be a little higher than yours.
IMR 4831 and RE-19 have worked best for me for velocity and accuracy with the bullets I have used.
I've noticed this too. My 7x64 runs slower than my .280 and the 7x64 has an extra inch of barrel. The 7x64 has a very long throat which may account for some of the loss in velocity. I built my 7x64 on a Ruger M77 tang safety action and seating the bullets out as far as the magazine box will allow is the best I can do. It is still the most accurate rifle I own though. I found with Re19 and H4831sc and 150gn Ballistic Tips I couldn't get enough powder in the case to get velocities up so came back to H4350. I haven't recovered a single 150gn Ballistic Tip yet. All have fully penetrated through pigs and fallow deer so far.
