Properly loaded, with 130 grain bullets, the 308 equals the 270 in velocity, and the 308 has 0.030" larger diameter bullets. The edge in killing power goes to the 308. The same applies to 150 grain bullets. And there isn't a 168 grain bullet for the 270. In fact the 160 grain 270 bullets are designed for the short magnum version, and a regular 270 will not send them down range fast enough for them to work properly. The 168 grain Sierra HPBTSP is recognized the world over as the most reliable and efficient projectile in the mid range cartridge class. It was designed for the 308. Further, the 308, for whatever reasons, apparently has the most stable and reliable external ballistics of any round in its class, which is why it has been adopted as both a target and sniper rifle by so many organizations and agencies. Most of those organizations and agencies can get anything they want, but they shoot 308.
I say that about a 308, and currently, I don't even own one, so I'm not "defending" my favorite rifle or cartridge. I may not buy another one, at least in a bolt action hunting rifle, because I already own Model 70 rifles chambered in 270, 30-06, and two in 300 Winchester Magnum. So I have three 30 caliber bolt action rifles (plus a 30-30) and the 270 Winchester. The 308 is within less than 10% of a 30-06, and the 270 is merely a necked down 30-06 with slightly less case volume (in most commercial cartridge cases). And I'm not saying the 270 is not an excellent cartridge, if I didn't think it was, I wouldn't own the rifle, a couple hundred rounds of ammunition, and everything required to reload it. I love my 270.
Any good centerfire rifle is adequate for deer, provided we're dealing with a skilled shooter. My old 220 Swift would kill deer like they were struck by lightning, if the shot was perfect.
In most places, there is not a shooting range, private or public, longer than 100 yards, within 50 miles of the average person's home. Therefore, the average shooter does not have a place to adequately practice shots of 200 yards or longer. The nearest available range to me is Oak Ridge, that's well over 100 miles, and isn't open on a regular basis, although it is a 1000 yard range. Most people do not have access to private lands with that sort of open range to practice on, either.
The 270 is more than adequate for deer and other game of that size or a bit larger, for exactly the range the person holding the rifle is up to the task.
I disagree with using the 270 on truly big game (deer are at best light skinned medium game with relatively small bones) because there are few, if any, bullets designed to break big bones and penetrate reliably. The power is there, the bullets are not.
Someone mentioned 100 grain bullets working better on deer than 140 grain bullets. They're using the wrong 140 grain bullet, and not getting expansion. It's not that the 140 is so fast, in fact, often the 100 is much faster, unless it is loaded down. It's that the 140 grain bullet is not expanding. Therein lies another problem with some smaller diameter bullets. If they don't hit bone in a light skinned animal, they often do not expand at all. This is especially true with some factory ammunition. At least if you start with a larger diameter bullet, at the same velocity, you get a larger hole, and a larger tissue disruption area. A good example of that is the difference between the bullets I use to hunt deer with a handgun, compared to the bullets I use to hunt boar or bear. For deer I use a 180 grain jacketed hollow cavity bullet at nearly 1800 fps muzzle velocity, because it expands rapidly and to over 50% greater diameter, and it does not need to hit any bone to do it. For bear and boar I use a 300 grain flat point solid lead bullet at around 1300 fps muzzle velocity. That bullet needs to penetrate deep, smashing bone if necessary, and the large flat nose disrupts tissue, because a bullet that expands easily on thick skin, dense tissue, or heavy bone, will not reliably penetrate deeply enough.
I'm not even suggesting "monster rifles" nor "magnum fever". I've never been a fan of that, especially for the vast majority of hunters, because they are not dedicated shooters. In fact, while I do own and shoot magnum rifles, I hesitate to suggest most people buy one. I suggest the 308 specifically because it has plenty of power, excellent accuracy, and well developed external ballistics tables, not to mention relatively light recoil and relatively low muzzle blast.
I'm not going to waste another second arguing about how well people shoot. I've hunted in a couple dozen states, and the same percentage of people who can't shoot well enough for the ranges they try to hunt at exist in every single one of them. It's a lot larger percentage than anyone wants to admit. Anyone who says it isn't is only fooling themselves. There is just as high a percentage of hunters over extending their skills in Wyoming, Colorado, or Idaho as there are here in Tennessee. The Bravo Sierra of "hunters here can shoot, the hunters around you suck" is just more ego stroking B.S., don't waste your time trying to sell that to me, I know better. I've been hunting and shooting for close to 40 years, reloading for nearly as long, and I was a wildlife tech for several years.
As far as saying "the 270 is barely adequate", that's not really what I said. And the average center fire rifle hunter is a far different hunter than those who hunt with "primitive weapons", although these days "primitive weapons" are far from being even remotely "primitive", and some of the same people who aren't ethical enough to be well practiced are now often found wandering about during archery and black powder seasons.
