I concure with 500 grains. Get it checked out by a Competent guns smith.
: It sounds as if you have a couple probems, but without seening the bolt, it is difficult to access.
: Generally, if there is galling on the cocking surfaces, lifting the bolt knob to cock the bolt (from fired position) will be bery difficult.
: These surfaces shouldn't be dry to start with, but also shouldn't gall. If there is a groove galled into the ramp surface, it sounds as if there is a flash chip on the other surface which is doing the cutting and that shouldn't be there.
: The safety in the middle position is the 'operating while cocked' location as it disengages the cocking surfaces. I didn't think the safety would go to that position if the bolt wasn't cocked. It's been a long time since I had a m70. Once cocked,the bolt's operation should be quite easy as well.