Yes, many and varied opinions and answers.
All-round for what
Varmints ?
Thin skinned game ?
African Antelope ?
North American Big game ?
Thick skinned and Dangerous game ?
I certainly wouldn't want to face an African Buffalo with anything less than a .375H&H or a 9.3 ,
but then I was brought up in Africa, and there aren't any Grizzlies there sitting on an ice floe waiting for their terminal 6.5x55 fix !
I guess we also tend to use what we've got, and justify that.
The Europeans shoot Moose with the 6.5mm, because that's their standard popular calibre, inherited from the Military.
I love shooting my .22 centrefires. They cover a wide range of 'small'ish' game, probably out to 250mtrs, but I wouldn't be shooting anything larger than a Goat, Roe, Muntjac, Duiker etc with them.
I'd more settle for a .243 for the small antelope sized thin skinned game, like Fallow, Springbok, the smaller Whitetail etc, javelinas and small hogs
,.....and then we probably start getting into the optimal 6.5mm and .30cal country, in my opinion,
esp for the larger deer and antelope.
but,
Anything that is capable of stomping, goring, biting, gouging or mauling me deserves something larger than .30cal,
even if it's just for respect !!!,
but then again if you can't handle recoil, don't go there.
Stick to hunting something less dangerous.
Nothing more disconcerting than a hunter flinching and blinking when in a tight spot,
but then I guess the guide behind him with the 4 bore Elephant gun has to earn his fee !!!
I have a lovely Sako 75 in .308 .
After years of loading Sierra's 155 and 175grs, and shooting Mil Surplus, Lapua 185 factory loads, and Federal Eagles I've just started shooting the 110gr V-Max in it for a lighter recoil load, and having plenty of fun. Accurate too. Recoil about 9/10 ft/lbs as opposed to 12/14.
Now you could class this as some sort of all-round calibre, (110gr - 180gr+) sort of a middle of the road allrounder,
but it depends what one intends to shoot with it, or what is available to shoot.
I respect the 6.5mm. Plenty of them about, esp the sporterised surplus Swedish Mausers, but I don't own one, and it's not on my 10 most wanted list.
I could use a 30/06 on big Reds, but the .308 would suffice.
30/06 seems to use a lot more powder, a large action, and generate more recoil for marginal increase in 'allroundness'.
In my opinion it's a matter of 'Horses for Courses' or....... 'Use enough Gun', as Ruark says.
cheers,
SS