I am going to take a guess that it is headspace issue but you still haven't said what cartridge you are shooting?
Out to 400 yards or so (farther really) the bullet that you use hunting doesn't mean a whole lot out of the tried and tested big game bullets. Accuracy is and always will be king. Since your bullets are touching at 100 yards, you have solved the accuracy issue (the most important), that is plenty accurate, so you you want to keep this ammo if at all possible. What we need to find out is if you are on the edge of over pressure. If there isn't any primer flow and maybe just some flattening, that is fine, I'll take that. If you can't get your bolt open, that's a problem.....
Again,is your bolt just a tad hard to open or do you have to beat on it to get it open? If it is just a tad stiff and there isn't primer flow, stay with the load. The load is telling you that it is on the edge of overpressure and you are getting about all you can out of it. A Chrono would help you solve this too....