Ft lbs of energy is a poor choice to compare cartridges. Especially when the lesser does the job fine AT THE RANGES THE PERSON SHOOTS. FPS of a cartridge will matter on long range shooting as well as the BC of the bullet. If all you are concerned about is ft lbs then get a larger bore cartridge. If comparing same caliber then by your standard he should get an Ultra-mag or Weatherby.
Then there is the matter of BULLETS. The bullets that one can use now are so much better than years ago that you do not need heavier or larger caliber bullets to get the job done cleanly. I am not talking about using a lesser caliber but that modern bullets of the same weight(or less) will now out perform bullets of the past. That is what Nosler Partition started years ago and it has grown into more top quality bullets.
Then there is the recoil/noise for the small gain between the 308 and 300mag AT THE RANGES HE SHOOTS and most game is usually taken---especially in Africa. Some cannot handle the recoil as well as others and a poorly placed shot with more ft lbs is really worse than a well placed shot with less.
I own a number of mags including a 300win mag but it tends to stay home and I will take my 308win or 30-06, if I choose 30cal, when I go hunting. Surprise: I have yet to not hit and kill my animal with the lesser rifles even at ranges out to 600 yards which is farther than I usually shoot.
Any energy that is expended AFTER leaving the animal is wasted energy. Ideally the bullet should expend all its energy in the animal and just exit and fall to the ground. Sometimes a bullet going too fast will not expand as well especially on small animals or not hitting bone. Just zips thru and does less damage than a slower one with less ft lbs. Kind of like what do you need a 1000hp/200mph car to sit in city traffic all the time and never go over 35mph?
Extra ft lbs can be good on some shots but the 308win has enough to do the job with a lot less noise/recoil and possible poor shot placement.
Sorry I do not buy your argument and I have been at this many years and own a number of hunting rifles/pistols.
Recoil is a very fair argument against the 300 win mag and above.
With the OP already having a very capable medium type of cartridge, I'm just thinking he doesn't need another that can do the exact same thing (7mm08, 270, 3006 for instance). If he wants another similar cartridge in which he loads one light load and one heavy load, sure, that's an option.
When I see a "2nd hunting rifle" thread, I try to fill in gaps. I could recommend a 243/6mm for the smaller animals, but I think he would be better served by going up instead of down for better reliability on large game.
You shoot a 300 pound animal square in the shoulder with a 308, they go down right there most of the time. Sometimes they make it 50 yards or so --- a long enough distances to potentially give you grief if you have ever had to pull one up out of a creek after he ran into it and died. A 7mag or 300mag would have flat out knocked him stupid.
You take an 800 pound animal and shoot him with a 308 - you may not be able to tell if it was hit. You shoot him a 300, you'll see a more pronounced stumble. Why? Because it hits it harder.
I agree you're going to get the same end result most of the time, probably 80-90% of the time. It's the other 10-20% I worry about with large animals.
We see reports written here all the time where someone made a decent shot (certainly not a bad one), they had some problems recovering, and they wished they would have used a bit more cartridge.
We'll have to agree to disagree
