Right after The .308 Winchester/7.62 NATO cartridge was developed, wildcatters went crazy with it, just like every other "new" cartridge case. They didn't have quite so much with this one, though, with it's already fairly sharp shoulder and minimal body taper.
What the did discover was that it was the right length for short action bolt guns and certain lever actions such as the Savage 99. The next thing the factories and wildcatters discovered was that with the advances in powder technology, they could get the original ballistics of the .30-06 our of the .308. Naturally, those same advances have brought the .30-06 into what was the .300 H&H territory but, really, those original .30-06, now .308 velocities are good enough for 95% of the hunting in the lower 48. Fact is, with some of the new bullets like the Swift A-Frame I would gladly swat a Moose with a .308. If there were any Moose in Texas. Excuse me while I look out the window. Nope, no Moose.Guess we'll have beef or chicken tonight, but, I digress.
Wildcatters and then, much later, the factories started churning out cartridges based on the .308. among the first were the .243 Winchester and the .358 Winchester. Meanwhile the wildcatters dreamed up things like the .25 Souper.
Meanwhile the rifle makers started making a whole slew of rifles built around two action lengths, one for the 53mm .308 case and one for the 63mm .30-06 case. Meanwhile this left the 57mm case of the Mauser rounds kind of out in the cold. You could barely fit them into the short actions, with lighter bullets, but not the longer, heavier bullets. And the actions built around the 63 mm case of the .30-06 (and the short Magnums like the 7mm, the .338 Winchester Mag and the .300 Winchester Mag) needed to have shims in the magazines to work with those 57mm cases.
The .243 Winchester became a very popular round, it is one of the best all around varmint rounds we can find, especially now that we have the 55 and 60 grain bullets. Now I never wanted to pop anything bigger', a groundchuck I'd be happy with a .222, .223 or even a .220 Swift. With larger varmints like the coyote or the bigger cats (although the Bambiest city folks have decided the cats are nice tame critters and need to be protected. Sure, they live in town where the big cats aren't. So, naturally, they know more than those of us who like in the country. I gotta admit, I am really getting sick of these self styled intellectuals who become experts on things they have never seen up close.)
The .343 is, with it's heaviest bullets, also a deer cartridge. Where it fails, there is that it is often given to young or beginning hunters, figuring that the light recoil will work for them. Well, yes, except that the .243, even with it's heaviest bullets is a professional's rifle, when it comes to light and medium big game. There just isn't the horsepower to take the tricky shots where we need a lot of penetration. And there aren't that many beginning hunters who know how to pass those shots.
This brings me to today's cartridge, the .260 Remington. This shoots a 6.5 mm bullet, just like the famous old 6.5mm Mannlicher. There was also a 6.5mm Mauser, a 6.5 Swede, etc. Back between about the Spanish American War to sometime after the end of the War To End All Wars (how'd that work out?) folks were taking those long 160 grain round nosed bullets and swatting everything up to Elephant with them. Oddly, if one was a very careful and skilled shot, and Elephant or a Cape Buffalo would fall right over. Of course, if one was not a very careful and skilled shot one had a very good chance of becoming part of the landscape. It is usually a good idea to avoid being trampled by those big critters.
WDM "Karamojo" Bell slew lord only knows how many Tuskers as an Ivory hunter using both the 6.5 and the 7mm Mauser. Back then the drill was to get up close and put the pill right where it would put the lights out. The reason most folks like the big guns like the .416 Rigby and .470 Nitro Express is that a bullet from one of those, an inch or two off, will stun Jumbo long enough for the insurance shot. Those smaller rounds, nope. And few folks really understand how fast they can move.
Today there is little need for those long, heavy bullets. Back then, the only way to assure deep penetration was to use a heavy bullet and what we now call a low velocity, somewhere between 2100 fps and 2400 fps. The bullets before John Nosler's Partition had trouble staying together at speeds much faster than that. So, we knew the bullets would lose weight, so, the heavier bullets had more weight they could lose. Today we seldom need anything heavier than the 140 grain premium bullets and, for deer and speed goats, the better 120 grain bullets are fine.
Now the .260 will do everything the bigger cartridges of that same caliber of a hundred years ago will do, it operates at a higher pressure. It's working pressure is over ten thousand pounds higher than the old Swede and nearly 20,000 higher than the Mannlichler. This is in part because of the advances in riflemaking and metallurgy since those old cartridges were new and party because no one knows the abuses some of those old rifles were put through.
If I were hunting with a .260 I would use the 95 and 100 grain bullets to pop the odd varmint and the 120 grain bullets for the smaller deer and Antelope. For the larger Mule Deer and those monster Yankee Whitetails I've read about but never seen, the 140 grain. I would save those 160 grain Hornady round nosed soft points for hunting where there might be a chance of bear or a Wapiti. And the reality is, one of the premium 140 grains will do as well.
There is much to be said for using just one bullet weight for all the big game hunting with a .260. Take the 140 grain. Small Deer and Antelope, use a standard bullet, the Hornady Spire Point, The Speer Hot Core, something along that line. In factory ammunition the Remington Core Loct or Winchester Power Point. The critter gets a little tougher? Try the Nosler AccuBond or Partition. bigger yet? The Swift A-Frame or Banes Triple Shock.
If I were just starting off as a young hunter I'd look long and hard at the the cartridges built around the .308 case. I would start with the .260, I'd look at the 7-08 and the .308. Which of those three I chose would depend on what critters were on the menu. If my hunting were deer and antelope I'd choose the .260 or the 7-08. If Wapiti or Moose were a possibility I'd look toward the .308. More hunters have hampered themselves through too much gun, too much recoil and muzzle blast leading to not enough accuracy. With the .260 this is not a problem.
With the exception of the Grizzly Bear of the Rockies, there is no critter in the lower 48 that will not fall to a .260 bullet suited for the game. Still, when we go above Mule Deer the .260 becomes an expert's weapon. The hunter needs to know the anatomy of the game and be willing to pass up the shots at difficult angles.
There has been a saying about hunting "use enough gun". Too often this has lead to using too much gun.The heaviest cartridge 95 percent of us will ever really need is around the 7mm Magnum or .30-06. Most of that 95 percent can go lower, down to the .260 or 7-08 level. Or the .250 Savage or any of a few dozen rounds between the .250 Savage and the .30-06. Got Grandpa Olav's 6.5 Swede? Great Uncle Heinrich's 7mm Mauser? Assuming they're in good shape, you're good to hunt just about anything but the great bears. and, tell you the truth, I'm not mad at any of the great bears. Of course, I don't live where they do, so there is that. I suspect if I lived up in Alaska in Brown Bear country I'd probably want to scrag enough of them to where they were a little leery about coming up to the door to beg a cup of sugar. We quit doing that with Mountain Lion and now, every once in a while they'll tear up and even kill someone. Oh well, what is a human being compared to making an "intellectual" happy.