I have a Marlin bolt gun- it isn't too picky about ammo, except it doesn't like the hyper-velocity stuff. I've got the best accuracy with Winchester Power Points (40 grain) and CCI Subsonic ammo. I use the subsonic stuff for pest control at close range when I need to be quieter, and it has worked very well for me, even for large varmits like groundhogs. However, you're not going to shoot 100 yards with it- 70 yards max.

The Power Points perform very well on game too, and have a bit more oompf. Even with these though, I've found that 100 yards is pushing it. Not because of lack of energy, but because of trajectory. It starts to drop off so much by then that you almost need a Mil-dot scope and a rangefinder. I usually sight in at 50 yards, then I'm only 1 or 2 inches low at 75 yards. After that, the drop just gets to be too much.