Compared: Standard Sevens
By Chuck Hawks
Next to .30 caliber (.308"), 7mm (.284") has become our most popular North American big game hunting caliber. There are at least four reasonably well known standard Sevens in North America and at least as many popular 7mm Magnums. Not bad for a European caliber with little market penetration in North America until the mid-20th Century. This article will take a comparative look at the cartridges named in the title. All of them have been covered in individual articles and even in previous comparisons, so I will keep the introductions short.
The 7mm-08 was standardized by Remington in 1980. It is simply the .308 Winchester case necked-down to accept 7mm 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 instead they got fancy and tried to achieve a little more case capacity by using a unique, fatter case body with a rebated rim and came up with the .284 Winchester.
As usual, Remington did a poor job of promoting their cartridge, but the 7mm-08 is so good that it gradually caught-on anyway and today 7mm-08 rifles and ammunition sell well. As I write these words, the 7mm-08 is the most popular of the standard 7mm cartridges in North America. It is available in most short action rifles, whether autoloading, lever or bolt action. It is at its best with 139-150 grain bullets and all of the factory loads from the major ammo companies use 139-140 grain bullets, except for a single Federal load with a 150 grain bullet.
An 1892 product of the famous Mauser Werke, the 7x57 is the cartridge that put the caliber on the map. In design, it is a thoroughly modern cartridge, despite its age. This is the cartridge that introduced the now "standard" rim diameter of .473" for rimless cartridges. It is an intermediate cartridge in overall length, since at the time of its development there were no short and long actions; actions were simply made to fit the cartridge, rather than to standardized lengths. Today, 7x57 rifles are generally built on .30-06 length actions. The 7x57 is the right overall length and has a long neck to take advantage of the entire range of 7mm bullets, from the lightest to the heavy 175 grain numbers; something that cannot be said for the short action Sevens.
Normally used today with 139-140 grain bullets for hunting CXP2 class game, the 7x57 is legendary in Africa, where it is often called the .275 Rigby, for hunting plains game. The commercial ivory hunter W.D.M. Bell used his 7x57 to kill something around 1000 elephants with brain shots, dramatic illustration that bullet placement is, by far, the biggest factor in killing power!
Winchester introduced the .284 in 1963 to give owners of the short action Model 100 autoloading and Model 88 lever action rifles .270-like ballistics. The cartridge was also briefly adapted to the Model 70 bolt action and the Savage Model 99 lever action. The .284 never really caught on and Winchester is the only major ammo manufacturer who has loaded for the caliber. Winchester still offers .284 brass and factory loaded ammunition and the .284 case is popular with cartridge wildcatters. In fact, today the 6.5mm-284 (recently standardized by Norma) is probably more popular than the original!
The .284 Winchester uses a unique case with an over size body and a rebated .473" diameter rim. This gives it similar powder capacity to the .270 Winchester and .280 Remington. Many hunters do not like rebated rim cases, because they decrease the feeding reliability of repeating rifles, and I am convinced that this is the reason for the .284's lack of popularity. On the other hand, the .284 is a better designed cartridge than the later 7mm WSM and 7mm Rem. SAUM, which also use rebated rims. It is an effective hunting cartridge, ballistically a short action .280 Remington, and still commercially available in one or two specialty rifles. Customers for custom built rifles who like something out of the ordinary sometimes commission a bespoke .284, so although ammunition sales are slow, they are enough to keep the cartridge alive. The .284 is at its best with 139-150 grain bullets and Winchester's sole remaining factory load uses a 150 grain bullet.
Remington created the .280 to compete with the famous .270 Winchester. Like the .270, the .280 is based on a necked-down .30-06 case and requires a standard length action. The .280's shoulder was moved slightly forward to prevent its accidentally being loaded and fired in a .270 rifle, where the larger diameter bullet would create excessive pressure. There is a comparison between the .270 and .280 on the Rifle Cartridges page, but suffice to say that what the .270 can do, the .280 can also do.
The .280 is a fine cartridge, but because it was introduced 32 years after the .270, it has never come close to matching the better established cartridge's popularity. Remington tried to correct this by changing the .280's name to "7mm Express Remington" for a time, but the name change accomplished little except to confuse potential customers and eventually Remington reverted back to the original .280 Remington nomenclature. Factory built rifles are available from Remington and occasionally other manufacturers. .280 ammunition is reasonably well distributed in North America. The .280 handles the long 160-175 grain 7mm bullets well, an advantage it has over the ballistically similar, but shorter, .284 Winchester.
These cartridges are all based on rimless cases with the same .473" rim diameter, as opposed to the .532" rim diameter used by most 7mm Magnums. The larger the case, the more powder a cartridge can hold and the faster it can drive a bullet at the same maximum average pressure (MAP). This puts the 7mm-08 and 7x57 at a disadvantage, because the .284 Win. and .280 Remington both have larger (.30-06 capacity) cases. The 7x57 is at a further disadvantage, because it is loaded to lower pressure in view of the antique rifles for which it was once chambered that cannot withstand modern operating pressures. Load a 7x57 to the same pressure as a 7mm-08 and it will outperform the newer cartridge, because it has a bit more powder capacity.
However, it is reasonable to ask how much performance is required and if the improvement in velocity, energy, trajectory and killing power that come with burning more powder at higher pressure are worth the extra recoil and muzzle blast that inevitably accompany higher performance. The modest 7x57, for example, has been used to kill every sort of big game animal, even elephants with 175 grain RN-FMJ bullets. Does hunting CXP2 game really require more power? 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.
139-140, 150-154, 160-162 and 175 grains are the most common bullet weights for these four cartridges. 7mm-08 factory loads are usually supplied with 139-140 grain bullets, because of that cartridge's short neck and modest powder capacity. In fact, 139-140 grains is an excellent general purpose bullet weight in all of these calibers and probably the most popular, so that is the bullet weight we will use for comparison.
In order to standardize the actual bullet, we will compare handloads using a Hornady 139 grain Spire Point InterLock bullet. The .284" diameter, 139 grain Hornady SP bullet has a ballistic coefficient of .392 and a sectional density of .246. This bullet will be driven by maximum powder charges in each caliber that essentially duplicate factory load ballistics. We will compare our typical loads in velocity, energy, trajectory, killing power and recoil. At the end of the comparison, I will offer some concluding observations.
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 standard 7mm cartridges at the muzzle, 100 yards, 200 yards and 300 yards with our 139 grain SP bullet and maximum 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 four cartridges, calculated for a telescopic sight mounted 1.5" over the bore and assuming a 200 yard zero.
These trajectories are surprisingly similar. A maximum difference of 1.9" in drop between the 7x57 and .280 is not a lot in terms of big game hunting, especially when you consider that the .280 is starting the same bullet 300 fps faster at the muzzle.
Killing power becomes crucial when you get your bullet into the animal's vitals. We all want humane, one shot kills. 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.
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.
It doesn't take a big increase in recoil to be noticeable. The 7x57, for example, subjectively (as well as actually) kicks less than the 7mm-08; the one ft. lb. difference is apparent to most shooters.
The 7x57 is a favorite here at Guns and Shooting Online. Its moderate recoil and substantial killing power has endeared it to generations of shooters. It is a classic African plains game cartridge, as well as a classic mountain rifle cartridge that is used by experienced sheep hunters around the world. In Europe and Africa, 7x57 ammunition is widely distributed and more available than the other standard sevens. The 7x57 is especially popular with the knowledgable hunters and shooters who patronize custom rifle makers. 7x57 factory built rifles are available in the US, but you may have to search to find one.
In the USA, the 7mm-08 is the best selling of the standard 7mm calibers; ammo and rifles in 7mm-08 are offered by most manufacturers. The 7mm-08 can be considered a short action 7x57, which explains its popularity. In modern rifles of equal strength loaded to the same MAP, there is practically no difference between the two and what advantage there is favors the 7x57. They are both excellent cartridges and when fired in standard weight rifles their recoil energy is below the 15 ft. lb. maximum that the majority of adult shooters find comfortable. Note, however, that ultra-light 7mm-08 rifles can generate uncomfortable recoil.
The .284 was designed as a short action .270 Winchester and the .280 was designed to compete head to head with the venerable .270. Neither has ever approached the popularity of the .270, but the .280 has been more successful than the obsolescent .284. The .280 handles bullets weighing from 139-175 grains well, a trait it shares with the 7x57. .280 rifles are not thick on the ground, but they are still factory produced and ammunition is reasonably well distributed, something that cannot be said for the .284 Win. .284 ammunition is typically in short supply and loaded only by Winchester in their Super-X brand, while .280 ammunition is a steady seller. My advice regarding these two cartridges is that if you think you need more performance than is offered by the 7x57 and 7mm-08, go with the .280 unless you must have a short action rifle.
Copyright 2010, 2012 by Chuck Hawks. All rights reserved.