Im more interested in killing the animal than just hitting it.

Although not being good for hunting, a possible setup has the bullet reaching the peak of its trajectory at the axis of the scope. However, I see your point in that in this setup, the bullet never crosses the scope axis. Still, it would be a single point along the trajectory where the scope axis and bullet trajectory are the same. If I'm reading the ballastics chart correctly on the Nikon SpotOn app, a 50 yard zero for a 30-30 with a 1.5 inch scope height would roughly create that type of trajectory.

But your point is well taken. A more distant zero appropriate for hunting requires a trajectory that crosses the scope axis twice. Case in point. A 150 yard zero for a 30-30 would follow a trajectory that crosses the scope axis when rising at 25 yards, and a second time when falling at 150 yards.

Gotta hit it to kill it.

no you got to hit it in the right spot

2" limit with factory ammo. That's good enough for normal hunting ranges.

That really depends upon what a "Normal Hunting Range" is to you and where you hunt.

I read a statistic a while back that the average distance for a shot on deer here in Virginia was something ridiculously close like 25 or 35 yards. Over half our state is shotgun only with more than a few counties allowing buckshot only in shotguns, farms and properties are small so I see where that statistic could be true. A gun that shoots a 10" group at 100 yards, like a bead sight, smooth bore 12 ga with slugs, will work just fine killing deer at 25 yards. For the places I hunt I don't need a rifle that shoots 1/2" groups at 100 yards and a 2" gun would be fine.

I'm sure that there are places in Texas that 200-300 yard shots are common with an occasional shot beyond that. A 2" group at 100 yards is a 6" group at 300. That means everything else about your hold, shot, wind and distance judging has to be about perfect to keep a bullet in the kill zone. I wouldn't want to count on a gun that groups 2" at 100 yards off a bench at the range to make a 300+ yard shot in the field.

Some people need to lighten up a little bit. Pretending that the "1.5" high at 100 yds" is not a proven way to kill game is just crazy. For over 30 years I sighted in my 7mags 3" high at 100. I managed to kill about 200 big game animals that way.

The MPBR method worked just fine for many, many years. Still does, last time I checked. Those who don't like it are free to not like it, but those who insist that it doesn't or can't work are not entitled to their own facts. BUT...it's just like anything else in this game: you gotta know what you're up against and what the limitations are. There's no place to go where you aren't bound by limitations.

Agreed. The Maximum Point Blank Range in based on the fact that because the bullet path and line of sight are the same at only two distinct points between the shooter and target. it only makes sense to choose a zero distance where ALL points along that range represent kill shots.

However, the question that remains is how much variance is acceptable for killing whitetails? In other words, what should be the maximum variation in the bullet's path above and below the line of sight?

Here's an example. Again, based on numbers from the Nikon SpotOn app, a 200 yard MPBR for a 30-30 would include a trajectory that's almost 3 inches high at 100 yards, and 2-1/2 inches low at 200 yards. The zero distance would be roughly 175 yards.

Would this variation be acceptable for killing whitetails?

The variance doesn't matter as long as the shooter knows the hold over/under and shoots enough to remember it. I don't personally use MPBR, but a lot of people do and have no problems with it. I zero my hunting rifles at 200 yards, but I'll be the last person to say that's the best way; it just works for me.
As far as the acceptable group size, 1.5" at 100 yards is acceptable for hunting IMO. If one of my rifles shoots 1.5" I do what I can to try to improve that group size. Acceptable is not a finishing point for me and I want to squeeze the best accuracy I can out of my rifles. That may or may not be MOA or sub MOA, but that's my goal.

That pretty much mirrors my approach to setting up a big game rifle. Works for me.

I don't disagree entirely. However, I have had experience that would suggest otherwise. I've set people up with such a rig, and with an adequate rest, had them banging the kill zone on the first shot at 300 yards.