aulrich
To my thinking, acceptable is a round that will consistantly provide an effecient death in a timely manner. Assuming the shot is placed in the vitals area of said game animal. Naturly a 22lr is acceptable for squirrel but not for black bear. Sure it will kill with a head shot, but good luck to the shooter. (or maybe not, might want them out of the gene pool.)
As far as a ft lb quote, those change a lot, but the common numbers now are 100 ft bs for deer and 1500 for elk. This is the minimum amount of energy remaining at point impact. So one must consider at what range you will limit yourself too with your particular cartridge and stay within that limit.
Common sense is the rule and maybe some have more than others, but by the same token, just because some choose to use nevk shots does not make their choice marginal.
I saw 2 perfect examples of a choice that illustrate.
On two separate outdoor shows I saw one guy take a 550yd shot at an elk, with a 300 Weatherby Mag. Problem was he hit the ground about 10ft in front of the elk on the first shot. He had no clue where to hold for that range. The elk took off at a trot and eventually a full gallop and said "hunter" was blasting away. Lucky for him, the elk ran closer to him and his FOURTH shot connected. Pittiful display of marksmanshipand sportsmanship.
The next one was a guy after black bear somewhere up north. This guy and his guide spot a trophy at a lasered 486yds out and is shooting, I think, a 300win mag. The bear was sitting on his rump facing the hunter, with his chest exposed.
Difference, is this guy has already been proven an excellent marksman and long range shooter. While standing with crossed shooting sticks, he nails this bear dead in the chest and you can see the dirt fly up behind the bear (an obvious pass through shot). This bear just slumps forward and rolls downhill dead.
My point? Great marksmen can make difficult shots seem normal and I for one won't question their ability to do so.