In y'all's opinion what is the maximum ethical effective range of a 45 caliber PRB on Whitetail deer?
That's a conscientious question, and there are two parts to your
ethical effective range question (imho) ...,
The .440 patched round ball, with 60-80 grains of 3Fg, will deliver lethal impact out to at least 100 yards on a whitetail deer. I'd be looking at a load between 70 -80 grains myself, but that's personal preference..., and would depend on the accuracy I found at the range.
The second part is...,
the accuracy of your particular rifle, and load, to 100 yards, or closer if your max shot is closer. For example, I have really good eyesight at distance, and so am very lucky. I can see the iron sights and the target out to 100 yards, but my 91 year old dad..., 50 yards is the limit as he cannot see the deer well enough to align the sights past that distance. What the ball will do is irrelevant as he can't employ his rifle past 50 yards.
(Of course, no harm no foul if one has to use modern optics on a traditional rifle to get the job done.)
IF you're like me and you hunt with a clean barrel, then at the range I'd test with a very clean barrel for each test shot, just to be sure.
I wouldn't be that concerned about the recoil vs. the stock on that rifle if you're using a patched round ball. You're reducing the recoil from a maxi-ball, which are 226 grains of lead, down to a .440 round ball which is about 126 - 127 grains, so you're reducing the projectile by 100 grains.
LD