I hunt in Darlington County and Williamsburg counties w/ a few visits to Orangeburg county every year. I shoot several different calibers for deer depending on the situation. My all purpose guns are .30-06 and .303 British. For field hunting and firebreaks, I'll use my 22-250. For brush, I'll pick up my SKS, or Mosin Nagant, or the NEF 45-70.
I have to disagree about the fatory loads. While they are purposely at the low end of the loading possibilities, that amount of power is more than sufficient to drop whitetails. Especially inside of 75 yds like this guy is hunting. Most of my shots are inside of 50 yds. I used to use level 2 handloads until I ran out one time and had to revert to the factory loads. I saw no noticeable difference in stopping power at these ranges. The bullets still went all the way through, opened an awesome wound channel, and didn't knock me senseless in the process.....
Now, w/ saying that.. If he is wanting to shoot longer distances w/ this rifle, he would probably want to get more potent loads to retain the velocity, but not at 75 yds......
Several manufactures do make ammo now only for the new 45-70's. They will have disclaimers all over them and some even designate the round 45-70 +P