Compared: The .270 Winchester and 7mm-08 Remington
By Chuck Hawks
The .270 Winchester should need no introduction to hunters. Introduced in 1925, it was formed by necking-down the .30-06 case to accept .277" diameter bullets. The .270 is the most popular of the 7mm class cartridges, although it is not a true 7mm; its bullet is .007" undersize. It is one of the great all-around cartridges and it is in widespread use wherever CXP2 and CXP3 game is hunted. Practically every hunting rifle with an action long enough to accommodate it is offered in .270 Winchester and virtually every ammo maker in the world loads .270 ammunition.
The 7mm-08 was standardized by Remington in 1980. It is simply the .308 Winchester case necked-down to accept 7mm (.284") bullets. This is a good idea, as it allows the use of bullets of similar weight and higher sectional density. The 7mm-08 is the cartridge that Winchester should have introduced back in 1963 for their short action rifles, but they got fancy and tried to achieve a little more case capacity by using a unique, fatter case body with a rebated rim for their .284 Winchester, which was a commercial failure. Savvy hunters (wisely) do not like rebated rim cases, because they decrease the feeding reliability of repeating rifles.
As usual, Remington did a poor job of promoting their new cartridge, but the 7mm is so good that it gradually caught-on anyway and today it is a top 30 best seller. It is available in most short action rifles, whether autoloading, lever or bolt action. All major ammunition manufacturers offer 7mm-08 loads.
The .270 and 7mm-08 are both based on rimless cases with the same .473" rim diameter and virtually the same head size. However, the .270 case is longer and this gives it more powder capacity. It is intended for use in standard (.30-06) length actions. The 7mm-08 is intended for use in short (.308 length) actions, which are generally about ½" shorter than standard length actions and consequently make for shorter and somewhat lighter rifles. Short action rifles are widely preferred for mountain and brush country hunting. However, understand from the outset that the .270's greater powder capacity makes it the more powerful cartridge with maximum loads. A glance at any ammunition catalog will demonstrate this, so the purpose of this comparison is not to determine which cartridge is more powerful. The .270 wins, end of story. However, it is reasonable to ask how much more powerful and if the improvement in velocity, energy, trajectory and killing power are worth the extra recoil and a longer, heavier rifle. The answer to that depends on the relative importance of these factors to the individual hunter; what this article will do is illustrate the differences so you can decide for yourself.
Typical factory loads from the major ammunition manufacturers are offered with 130, 140 and 150 grain bullets in .270 Winchester, while almost all 7mm-08 factory loads use 139-140 grain bullets. 130 grains is the traditional .270 bullet weight and a 130 grain .270 bullet has a sectional density (SD) of .242, good for general purpose hunting of thin-skinned game. A 139 grain 7mm bullet has a SD of .246, which is very similar. Comparing bullets based on SD is a better (more equal) method than using the more obvious bullet weight, since it is SD, not bullet weight, which determines penetration (all other factors being equal, of course).
In order to standardize the actual bullets, we will compare loads using Hornady Spire Point InterLock bullets in both calibers, 130 grains in .270 (BC .409) and 139 grains in 7mm-08 (BC .392). Typical muzzle velocities for both factory loads and handloads are about 3060 fps for the 130 grain .270 bullet and 2800 fps for the 139 grain 7mm-08 bullet, so those are the specific velocities we will compare. We will compare our typical loads in velocity, energy, trajectory, cross-sectional area, killing power and recoil. At the end will be a short summary and conclusion.
Velocity matters because it flattens trajectory and increases the energy delivered to the target. Here are the velocity figures in feet-per-second for our cartridges at the muzzle, 100 yards, 200 yards and 300 yards with our selected loads.
Energy is an important factor in killing power. It is what powers bullet penetration and expansion. Here are the energy figures in foot-pounds for our comparison loads at the muzzle, 100 yards, 200 yards and 300 yards.
Trajectory is important because the flatter a bullet shoots, the easier it is to hit with as the range increases. Bullet placement is, by far, the most important aspect of killing power. Here are the trajectories in inches for our two cartridges, calculated for a telescopic sight mounted 1.5" over the bore and assuming a 200 yard zero.
Bullet frontal area is an important element in the killing power of rifle bullets. Other factors being equal, the bigger the diameter of the bullet, the bigger the diameter of the wound channel it makes and the more tissue destruction it causes. In this area, the 7mm has a small advantage over the .270.
We all want humane, one shot kills, so killing power is extremely important. There are many ways to measure killing power and one of the newest and best is the Hornady Index of Terminal Standards (HITS). The HITS formula considers energy, bullet weight, sectional density, ballistic coefficient and impact velocity to derive a killing power rating at 100 yards. The HITS ratings fall into one of four categories, as follows: Small game (weighing under 50 pounds) = less than 500 HITS; Medium game (50-300 pounds) = 500-900 HITS; Large game (300-2000 pounds) = 901-1500 HITS; Dangerous game (any species, no weight restrictions) = 1500+ HITS. Here are the HITS numbers for our selected loads.
This is where the 7mm-08 shines in comparison to the .270. Recoil interferes with accurate bullet placement. Everyone can shoot better with a rifle that kicks less. Increased performance means increased recoil; you can't cheat the laws of physics. Here are the recoil energy (ft. lbs.) and velocity (fps) figures for our comparison loads, calculated for eight pound rifles.
Bear in mind that, while most experienced shooters can tolerate recoil energy up to about 20 ft. lbs., 15 ft. lbs. is about the maximum amount of kick with which most shooters are actually comfortable. Rifles that deliver more than approximately 15 ft. lbs. are not much fun to shoot at the rifle range. Consequently, they usually get less use than rifles that kick less.
Summary and Conclusion
As demonstrated by the comparison above, the .270 Winchester is somewhat superior in most performance categories. Of course, we knew that going in. The real question is whether it is superior enough to justify the discomfort of its greater recoil. There is little difference between the two cartridges in killing power, so that will probably not be the deciding factor. The biggest difference is in trajectory. The 130 grain .270 load has a maximum point blank range of approximately 300 yards, so if long shots are common in your area, the .270 would be preferred.
For short and medium range hunting, it makes sense to take advantage of the lower recoil (and 1/2" shorter rifle for slightly faster handling) offered by the 7mm-08. Note, however, that ultra-light rifles in either caliber can generate uncomfortable recoil. Keep rifle's scoped and loaded weight at, or above, eight pounds for best results with both cartridges.
Copyright 2010, 2012 by Chuck Hawks. All rights reserved.