Compared: .270 Winchester and .30-06 Springfield
By Chuck Hawks
These are two of the best selling centerfire rifle cartridges in the world. For bolt action hunting rifles, the .30-06 is #1 in sales, and the .270 Win. is #2. The .270 has been the most successful cartridge to challenge to the popularity of the .30-06, but it has never quite caught up with the rival whose case it shares.
Both cartridges are based on the same case, which dates back to the .30-03 cartridge, adopted by the U.S. Army in 1903. The .30-06 is the .30-03 case with its neck shortened a bit (.30-06 cartridges can be fired in .30-03 rifles), and the .270 Winchester is simply a .30-06 case necked down to accept .277" bullets instead of .308" bullets, retaining the same 17.5 degree shoulder angle. Both cartridges are covered in detail in articles on the Rifle Cartridge Page, so I will skip lengthy descriptions of them here. (Both are also included in "The Great All-Around Rifle Cartridge Comparison" on the Rifle Cartridge Page.) The powder capacity of the .270 and the .30-06 cases is essentially the same, and the cartridges are dimensionally the same except for neck and bullet diameter. The same headspace gauge works for both calibers.
The .270 Winchester
Winchester introduced the famous .270 in 1925 to an indifferent shooting world that initially took little notice of the new cartridge. For decades after its introduction it was the highest velocity, flattest shooting big game cartridge available from a major manufacturer. A number of gun writers, including Jack O'Connor "the Dean of American Gun Writers," liked the .270 and sang its praises.
As the years went by .270 rifle and ammunition sales gradually increased until, ultimately, it became a best seller and the standard of comparison among long range big game cartridges. .270 Winchester ammunition is manufactured and used worldwide. The cartridge is available in practically every hunting rifle with an action long enough to accept it, including bolt, lever, pump, autoloading, and single shot models.
The .30-06 Springfield
This number was adopted by the U.S. Army as the "Ball Cartridge, Caliber .30, Model of 1906," but quickly became universally known as the ".30-06." The .30-06 is the best known big game hunting cartridge in the world. It has been used on every species of North American, Asian, European, and African big game and has probably killed more CXP2 and CXP3 class game world wide than any other cartridge.
The .30-06 served the U.S. very successfully through two World Wars and the Korean War. Like the .270, it requires a long action rifle, which was why it was finally replaced in military service by the .308 Winchester (7.65mm NATO) in 1954. But in the game fields of the world it has yet to be replaced by any other cartridge. Like the .270, .30-06 ammunition is manufactured and used all over the world and the cartridge is available in rifles of all types.
It is no wonder that the .270 and 30-06 have been compared and debated by big game hunters for over 80 years. The common bullet weight shared by both calibers is 150 grains. This has caused most shooters to compare the two calibers with that bullet weight, often with misleading results.
The proper way to compare bullets of different diameter but similar purpose (in this case big game hunting) is by sectional density (SD), and that it what we will do here. Hopefully, we will be able to shed some light on the matter.
Sectional density is defined as a bullet's weight (in pounds) divided by the square of its diameter (in inches). If you compare two bullets of the same weight but different calibers, such as 150 grain .270 and .30 caliber bullets, the smaller diameter bullet will be longer and have a higher SD. The actual SD numbers for those two bullets are .279 (.270/150) and .226 (.30/150), which is a big difference in SD. It is thus unrealistic to compare 150 grain bullets in .270 Win. and .30-06. More on sectional density later.
The 130 grain .270 bullet has a SD of .242. The nearest comparable bullet weight for the .30-06 is 165 grains, which has a SD of .248. The 150 grain .270 bullet has a SD of .279. The closest .30-06 bullet is the 180 grain, which has a SD of .271. These are the bullet weights that we will compare in this article.
Of course, more than SD and bullet weight enters into any hunting cartridge comparison. We will also compare bullet cross-sectional area, velocity, energy, trajectory, killing power, and recoil. The availability of rifles and ammunition is so good in both calibers that for our purposes they can be disregarded.
Most manufacturers of factory loaded ammunition offer loads using the selected bullet weights. There is, in fact, an embarrassment of .270 Winchester and .30-06 factory loads.
Remington loads their popular Core-Lokt bullets in both weights for both calibers, and publishes the ballistic coefficients of their bullets. So for uniformity and convenience, I chose Remington Express factory loads using Core-Lokt bullets for comparison. The selected Remington Express .270/130 and .30-06/165 grain loads use Core-Lokt Pointed Soft Point (spitzer) bullets. The selected Remington .270/150 and .30-06/180 grain loads use Core-Lokt Soft Point (round nose) bullets. The results with equivalent loads from other brands would be similar.
Sectional density and ballistic coefficient
Sectional density is important because the greater the SD, the longer a bullet is for its weight and, other factors being equal, a long skinny bullet of any given weight penetrates better than a short fat bullet of the same weight. Penetration is an important factor in the length of the wound channel, the amount of tissue disrupted and destroyed, and thus killing power. That explains why the 150 grain .270 bullet is a better choice for hunting large animals than the 150 grain .30-06 bullet, and why the two are not really comparable.
Although a bullet's shape is not a factor in calculating sectional density, bullets with a higher SD also tend to have a higher Ballistic coefficient (BC) when of similar form. BC is a measurement of how well a bullet flies through the air. The higher the BC, the more aerodynamic the bullet and the lower its drag.
A higher BC helps a bullet retain more of its initial velocity and energy down range and results in a flatter trajectory. Here are the sectional densities and Remington's published ballistic coefficients for the four bullets used in the loads compared in this article.
As you can see, the .270/130 and .30-06/165 grain bullets are very similar in BC, while the .270/150 and .30-06/180 grain bullets vary a bit. This is partly because the .270 has a somewhat superior SD, and mostly because Remington chose a somewhat broader nose profile for the .30 caliber bullet. It is practically impossible to find popular bullet weights in .270 and .30 calibers that are identical in SD and BC. Never the less, these bullets are similar enough to make a worthwhile comparison.
Given bullets of identical construction, and other factors being equal, the 130 grain .270 and 165 grain .30-06 bullets should offer similar penetration. Ditto for the 150 grain .270 and 180 grain .30-06 bullets.
In a practical sense this means that if a given 180 grain .30-06 bullet will shoot through both shoulders of a grizzly bear, so will a 150 grain .270 bullet of the same design and construction. And if the 165 grain Core-Lokt .30-06 bullet gives adequate penetration for broadside lung shots on elk, then so will the 130 grain Core-Lokt .270 bullet (it does!).
Bullet cross-sectional area
The cross-sectional area of a hunting bullet is important because, other factors being equal, the fatter bullet makes a wider wound channel and damages more tissue. This translates to quicker and more humane kills. Bullet weight has no bearing on frontal area, only caliber. The actual bullet diameter of .270 Winchester bullets is .277"; the diameter of .30-06 bullets is .308". Here are the frontal areas of each:
As those numbers reveal, the .30-06 has a clear advantage over the .270 in bullet frontal area. This potential for a wider wound channel is probably the single most important reason for the perception that .30 caliber rifles kill better than the smaller calibers, and it constitutes a real advantage for the .30-06.
Higher velocity means flatter trajectory, given bullets of equal ballistic coefficient (BC). Velocity is also an important component in the formula used to compute kinetic energy. And impact velocity may influence killing power. (The later assertion is widely debated and is almost always good for a lively discussion in hunting camp.) Here are the Remington velocity figures from the muzzle (MV) to 400 yards in feet-per-second for our selected .270 Win. and .30-06 loads, taken in 24" test barrels.
Clearly the .270 has a considerable advantage in velocity at all ranges when bullets of similar SD and BC are compared. It should come as no surprise that the .270/130, the classic long range hunting load, is the fastest in our comparison.
Note that the .270/150 bullet starts faster than the .30-06/165. If we were comparing spitzer bullets of similar form, the .270/150 would retain its initial velocity advantage--and shoot flatter--than the .30-06/165 all the way down range.
Kinetic energy is a measure of the ability to do work. The "work" in this case is penetrating deep into a game animal and powering bullet expansion. The key factors in computing kinetic energy are bullet mass and bullet velocity squared.
Energy is an important factor in bullet performance and killing power. Despite criticisms of energy as a comparative tool by some "experts," it is a good indicator of the power of similar rifle cartridges. Here are the Remington energy figures for our selected loads in foot-pounds from the muzzle (ME) to 400 yards.
The 165 grain .30-06 load shows a modest advantage in energy compared to the 130 grain .270 load, ranging from 170 ft. lbs. at the muzzle to only 40 ft. lbs. at 400 yards. The .30-06's advantage at 200 yards is 91 ft. lbs., or about 5% more energy than the .270/130 load.
The heavy 180 grain .30-06 bullet develops the most muzzle energy of any of our loads, but by the time that bullet has reached100 yards its retained energy has dropped below that of the 165 grain .30-06 load and the 130 grain .270 load. This is because it is a round nose bullet. As the range increases, the lighter spitzer bullets' advantage in retained energy increases. This is due to the higher BC of the PSP bullets, and clearly illustrates why pointed bullets are the proper choice for long range shooting.
From the muzzle to 300 yards, the .30-06/180 load retains more energy than the .270/150 load. At 300 yards the .270/150 and .30-06/180 loads are about equal in kinetic energy, and at 400 yards the .270 load actually has a slight advantage. The heavy, round nose bullets are a good choice for penetrating brush and hit hard at short range (less than 100 yards), but quickly lose their advantage as the range increases. Overall, the .30-06 loads deliver slightly more energy than the equivalent .270 loads.
Trajectory is important to hunters because the flatter a bullet's trajectory, the easier it is to achieve precise bullet placement at long and unknown ranges. And bullet placement is, by far, the most important factor in killing power. The primary factors influencing trajectory are bullet velocity and ballistic coefficient.
Ammunition catalogs usually show bullet drop from 100 to 500 yards with a 200 yard zero, and that is the way Remington compares our selected loads. Here are the published trajectories for our loads (in inches above or below the line of sight of a scope mounted 1.5" above the bore) out to 400 yards.
The higher velocity of the .270 pays dividends in flatter trajectory across the board. At 400 yards the .270/130 has 5" less drop than the .30-06/165 load. And at the same distance the .270/150 has 5.2" less drop than the equivalent .30-06/180 load.
How much this flatter trajectory matters depends on your style of hunting. I would suggest limiting shots to no more than about 225-230 yards with either of the round nose bullets, and no more than around 250 yards for the .30-06/165 or 275 yards for the .270/130 when zeroed at 200 yards.
Killing power is the most difficult factor to quantify. Bullet placement is the most important factor in a cartridge's effectiveness on game, and that is largely a function of the shooter's skill and judgment, not the cartridge used. The construction and performance of a hunting bullet is also very important, and practically every type of hunting bullet is available for either the .270 or the .30-06. Kinetic energy is one indication of potential killing power, as are bullet frontal area and sectional density, but none of these tells the entire story.
One attempt to include at least some of the relevant factors (primarily impact velocity and bullet weight) is the Optimum Game Weight (OGW) formula developed by Edward A. Matunas and published in the Lyman 47th Reloading Manual. Matunas assumed that bullet design and placement are adequate for the task at hand. I believe that these OGW figures are based on spitzer bullets in all weights, not the round nose bullets we have previously used for comparison in the .270/150 and .30-06/180 loads.
Here are the OGW figures in yards for typical .270 Win. and .30-06 big game loads. (For more on OGW, see the "Expanded Optimum Game Weight Table" on the Tables, Charts, and Lists Page.)
Another way to compare killing power is by using the Rifle Cartridge Killing Power Formula developed by yours truly. It at least attempts to include the factors of energy at 100 yards (which incorporates velocity), sectional density (which incorporates bullet weight), and the bullet cross-sectional area of various calibers and loads in a formula that gives a simple number that allows comparisons to be made. (You can read more about the Rifle Cartridge Killing Power Formula and compare dozens of calibers and loads in the article on the subject included on the Tables, Charts and Lists Page.) Here are the results for typical .270 and .30-06 loads at 100 yards. Just for comparison, I have added the numbers for typical .243 Win./100 grain and .338 Win. Mag/250 grain loads.
By either system, the .30-06 comes out ahead of the .270 in killing power. Whether the difference is significant in the real world is debatable. Fans of the .270 claim that it isn't, while fans of the .30-06 think that it is. Jack O'Connor, who had very extensive experience with both calibers on game animals all over the world, wrote that he failed to see a significant difference in killing power between the 130 grain .270 load and the 180 grain .30-06 load.
The recoil generated by any rifle/cartridge combination is very important regardless of the courage, size or strength of the shooter. Virtually everyone can shoot more accurately with a rifle that kicks less. This is true even for experts. The best shooting is done with the rifles that kick the least; just look at the results from practically any of the target shooting games for confirmation.
Remember that bullet placement is, by far, the most important ingredient in killing power. And no one can consistently put a bullet into the vitals of a game animal with a rifle that causes them to flinch. Here are recoil numbers for our various loads calculated by the Remington Shoot! program for rifles weighing a uniform 8 pounds.
In terms of recoil energy, the .270 is the winner with each bullet weight, although neither of these cartridges is a particularly light kicker in standard weight rifles. All loads are above the 15 ft. lbs. limit recommended for consistent accuracy, but below the 20 ft. lb. "do not exceed" level. Rifles weighing less than 8 pounds (including scope) in both .270 Win. and .30-06 should be avoided.
The great Jack O'Connor once wrote that if only the .270/130 grain and .30-06/180 grain loads were available we would all do just fine, and I am inclined to believe that he was right. I think that these are the loads that most clearly differentiate the two cartridges. In fact, my .270 is zeroed for the 130 grain load and my .30-06 is zeroed for the 180 grain load, albeit the PSP (spitzer) rather than the SP (RN) version. A spitzer bullet is the best choice for an all-around rifle, while the RN bullet is the best choice for hunting in heavy woods or brush, and possibly for large, dangerous game.
The spitzer bullet extends the maximum point blank range (+/- 3") of the 180 grain .30-06 load to around 263 yards. The MPBR of the .270/130, for comparison, is close to 300 yards, depending on the exact MV and BC of the bullet used.
I think that the .270 gives quicker kills on CXP2 game and that the .30-06 does the same on CXP3 game. But if I got a clear shot at an elk when I happened to be carrying the .270/130 on a mixed bag hunt I would take it, just as I would take a shot at a deer with the .30-06/180 under the same circumstances.
Copyright 2006, 2012 by Chuck Hawks. All rights reserved.