Here's a good read, just take it as you will.
http://www.chuckhawks.com/270family.htm
The .270 Family of Cartridges
By Chuck Hawks
There is no magic caliber, and no magic bullet. If there were I would be inclined to nominate the .270 caliber and the 130 grain bullet for the honors. Perhaps no other caliber has compiled, with a single bullet weight, such an outstanding record on such a variety of animals at all ranges. The key to the success of all four of the principal .270 calibers is a blend of flat trajectory coupled with versatility and manageable recoil that is pretty hard to match, let alone beat.
Despite the amount of favorable press devoted to the 7mm cartridges, in North America at least, they have always existed in the shadow of the .270 calibers. The .270 Winchester has out sold all of the standard 7mm cartridges (and especially its main rival the .280 Remington) by a wide margin, the .270 Weatherby Magnum has traditionally outsold the 7mm Weatherby Magnum and the .270 WSM is outselling the 7mm WSM. The new 6.8mm Remington SPC, the obsolete .30 Remington case necked down to .270, is practically guaranteed to outsell the neglected 7-30 Waters (based on a necked-down .30-30 case). A clean sweep, so to speak.
For many years there was no real .270 family of cartridges, only the original .270 Winchester and a couple of wildcats. Winchester created the .270 by simply necking down the .30-06 case to accept .277 inch bullets. For many years it was the high velocity king of commercial big game rifle cartridges. The .270 Winchester was (and is) so good at being a combination long range and all-around cartridge that perhaps no other cartridge in the caliber was necessary. Given the powders available in 1925, the year of its introduction, perhaps no better long range cartridge was possible.
Not until 1943 was another commercially successful .270 cartridge designed. This was the .270 Weatherby Magnum, which went commercial a few years later. The .270 Weatherby is based on a blown-out .300 H&H Magnum case shortened to fit standard (.30-06) length actions.
To underscore the importance of the .270 Weatherby Magnum it is worth noting that it was the first of Roy Weatherby's magnum cartridge series. Roy considered the .270 so important that is where he started. All of the other Weatherby Magnums, the .257 and 7mm (based on the .270 case), and the long .300 and subsequent famous Weatherby Magnums, came after the .270.
The .270 Weatherby Magnum took advantage of its big case to launch a 130 grain bullet about 200 fps faster than possible from the .270 Winchester. The .270 Weatherby remains the top performing standardized cartridge in the caliber. Once considered overbore, the advent of very slow burning powders like H870, IMR-7828, and RL22/Norma MRP make the .270 Weatherby Magnum in a 26 inch barrel very hard to beat.
One of the latest members of the .270 family is the .270 WSM. This cartridge is based on the short but very fat .300 WSM case necked down to accept standard .277 inch bullets. It was immediately successful, as it filled the need for a short action .270 caliber cartridge. In performance this short magnum cartridge falls between the standard length .270 Winchester and .270 Weatherby Magnum.
The newest member of the .270 clan is the short (.223 length) 6.8mm Remington SPC. It also uses standard .277" bullets and was designed to supplement the maligned 5.56mm NATO service cartridge. Remington, who participated in the design of the new cartridge, has introduced it to the civilian market as the 6.8mm Remington SPC. Initial factory loads drive a 115 grain bullet at a MV of 2800 fps with ME of 2002 ft. lbs. It is reputed to be a fine target round. The 6.8mm SPC also promises to be a good, low recoil, deer and antelope cartridge along the lines of the 7-30 Waters.
Those are the members of the small but very successful commercial .270 family. All use .277 inch diameter bullets. Probably because of their relatively moderate recoil, all four of the commercial .270 caliber cartridges have earned a fine reputation for excellent accuracy.
The traditional .270 bullet weights for big game hunting are 120-150 grains. For varmint and small predator shooting the common bullet weights are 90, 100 and 110 grains. Occasionally one encounters 115, 170 and 180 grain bullets, but these are relatively rare. There isn't much that a .270 rifle can reasonably be called upon to do that cannot be accomplished with the more popular bullet weights. With such a wide assortment of bullets available to the reloader, strong cases, and an assortment of modern slow burning powders, .270 is one of the easiest and most popular calibers for which to reload.
Probably the most important factor in the success of the commercial .270's is their high velocity. For many years the standard .270 Winchester factory load drove a 130 grain spitzer bullet at an honest muzzle velocity (MV) of 3140 fps. For unexplained reasons the ammo manufacturers have recently backed off their .270 loads--perhaps to sell more magnums; current catalog MV is 3060 fps. Handloaders can still duplicate the original load. The .270 WSM advertises a MV of 3275 fps with the 130 grain bullet, and the .270 Weatherby features a MV of 3375 fps with the same weight bullet. Even the little 6.8mm SPC has an advertised MV of 2800 fps.
The full size .270 cartridges deliver high velocity with big game hunting weight bullets, and since kinetic energy is basically a function of bullet weight times velocity squared, these high velocities mean that there is plenty of downrange energy to initiate bullet expansion and inflict fatal damage on the target.
High velocity also makes for flat trajectory and an extended maximum point blank range (MPBR), which makes accurate bullet placement easier. And bullet placement is always the most important factor in killing power.
The good sectional density (SD) of the popular 130, 140, and 150 grain bullets also contributes to the cartridges' killing power. To kill quickly a bullet must penetrate deep into an animal's vitals, and sectional density is an important factor in penetration (as, of course, is adequate bullet design).
The 130 grain .270 bullet has a SD of .242. This is identical to the 100 grain .243 bullet (also noted for deep penetration) and similar to the 140 grain 7mm and 165 grain .30 caliber bullets. It is considerably superior to the 150 grain .30 caliber bullet (SD .226) to which the 130 grain .270 load is often mistakenly compared.
The 140 grain .270 bullet has a SD of .261. This is similar to the 120 grain .25 caliber, 129 grain 6.5mm, and 170 grain .30 caliber bullets.
The 150 grain .270 bullet has a SD of .279. This is similar to other bullets famous for deep penetration such as the 160 grain 7mm bullet, the 180 grain .30 caliber bullet, and the 250 grain .35 caliber bullet.
The long 160 grain bullet has a SD of .298. This is comparable to the heavy 175 grain 7mm bullet, 200 grain .30 bullet, or 220 grain 8mm bullet. According to the Nosler Reloading Guide this bullet can be driven to over 2800 fps in the standard .270 Winchester or 3100 fps in the .270 Weatherby Magnum. Zowie!
Perhaps these figures and comparisons, when coupled with the high velocity and excellent down range energy delivered by all of the .270 cartridges, begin to explain their excellent killing power.
Moderate recoil also plays a part in the .270 story. Practical accuracy, as opposed to intrinsic accuracy, has to do with how well the shooter can actually shoot his or her rifle. And the more that rifle kicks, the harder it is to shoot accurately. It is here that the little 6.8mm Remington SPC really shines. It is one of the lightest kicking deer cartridges to throw a full diameter hunting bullet and one of the lightest kicking cartridges suitable for CXP2 class game.
None of the standard length .270 calibers could be called light kicking calibers in normal weight rifles, but they do kick less than the 7mm and .30 caliber rifles to which they are usually compared. For instance, in rifles of the same weight and shooting bullets of the similar sectional density loaded to the same pressure, the .270 Winchester kicks less than the .280 Remington or .30-06 Springfield. Likewise, the .270 WSM kicks a little less than the 7mm WSM, 7mm Rem. SAUM, or any of the .300 short magnums. And the .270 Weatherby Magnum kicks a little less than the 7mm Weatherby Magnum and much less than the .300 Weatherby Magnum.
All four of the commercial .270 cartridges are covered in individual articles, which can be found on the Rifle Cartridge Page of Guns and Shooting Online. But, before I conclude this little overview of .270 cartridges it might be interesting to take a brief look at a couple of wildcat .270 cartridges.
Historically, the most useful wildcat .270 is probably the .270 Savage. The .270 Savage was designed to provide a short action .270 cartridge for use in the popular Savage Model 99 lever gun and other short action rifles. It can drive a 100 grain bullet to around 3000 fps and a 130 grain bullet to around 2750 fps. Heavier bullets intrude too far into the powder space and are not usually recommended. As wildcats go, the .270 Savage had a pretty good run. With the advent of the commercially available 7mm-08 Remington, the .270 Savage is no longer necessary.
Another interesting wildcat is the much more recent .270 REN. Charles Rensing and Jim Rock designed this little cartridge specifically for NRA Hunter Pistol Silhouette competition. It is based on the .22 Hornet case necked-up to a straight wall configuration. It is reloaded with 90-110 grain bullets with velocities in the 1600-1875 fps vicinity. Recoil is very low, and Merrill and Thompson/Center have offered guns in .270 REN. A T/C Contender Carbine or Encore single shot rifle in .270 REN would make an interesting and unusual alternative to a .25-20, .30 Carbine, or .32-20 rifle.
This then is the modern .270 caliber family. It is not extensive, but it is very successful. There is a .270 cartridge for just about every taste, in short, standard, short magnum, and standard length magnum forms.
