7mm Remington Magnum
By Nathan Foster
When the Mauser brothers designed the 7x57 cartridge for use in their M93 military bolt action rifle, the excellent qualities inherent in the 7mm bore diameter soon became apparent to cartridge designers all over the world. Here was a cartridge that produced a flatter trajectory than most of its competition, minimal wind drift and potentially, optimum terminal performance at extended ranges. Following these discoveries, cartridge designers began to experiment with larger cases to maximize down range performance.
One of the earliest high power designs was the .280 Ross, designed by F.W Jones for the Ross rifle company of Quebec, Canada in 1906. This cartridge featured a rimless case, not too dissimilar to the 7mmRUM. The Ross rifle and cartridge were intended primarily for military use however the rifle locking mechanism had some short comings which proved undesirable.
The British were also very interested in driving 7mm bullets at maximum velocities. Holland & Holland introduced the .275 H&H Magnum in 1912, based on a shortened version (2.5”) of their .375 H&H cartridge case, featuring the typical H&H smooth feeding tapered case deign. The British military tried to follow on from this with the creation of the .276 Enfield prototype cartridge and P14 rifle to house the large 7mm magnum. Unfortunately for Enfield designers, war and politics halted any further experimentation. These early cartridges, the Ross, H&H and Enfield generally achieved 2900fps with 140 grain bullets. Higher velocities were not quite yet obtainable due to the limits of powder design. Throat erosion was also very severe.
The first truly potent magnum sevens to be created were the 7x61 Sharp and Hart and the 7mm Weatherby magnum, both U.S inventions, introduced during the early 1950’s. While the cartridge designs were somewhat similar to the .275 H&H, albeit blown out to minimize body taper, the major breakthrough was the adoption of surplus 20mm cannon powder. This slow burning powder enabled huge increases in velocity. Nevertheless, although the 7x61 and Weatherby were very good cartridges, neither had become mainstream offerings which limited ammunition availability and effected pricing.
Following the introduction of the 7mm Weatherby and 7x61, American gun writer Warren Page of 'Field & Stream' magazine was noted, among others, for promoting the idea that America needed a standardized Magnum 7mm cartridge chambered in a standard production rifle, easily obtainable from any gun store. Wildcatter Art Mashburn had recently designed a very appealing candidate based on the .300 (or .375) H&H case necked down to 7mm, this was similar to the 7x61 and Weatherby however rather than being shortened to 2.5”, the Mashburn featured a longer case at 2.620” as opposed to 2.5” resulting in a noticeable increase in powder capacity.
Warren Page had Art Mashburn chamber one of his rifles for the 7mm Mashburn Super Magnum and Page was ecstatic over the results. The Mashburn was able to drive a 160 grain bullet at 3200fps and for medium game hunting at both close and longer ranges, the Mashburn was an emphatic killer.
The situation became heated when Jack O'Connor gifted his .275 H&H magnum (load at the time was a 175 grain bullet at 2680fps) to wildcatter Les Bowman. Impressed with the idea of a 7mm magnum, Bowman in turn had a .338 Win Mag necked down to 7mm by Fred Huntington of RCBS, naming it the .280 Remington Magnum. Bowman had no trouble impressing his friend Mike Walker of Remington with the new cartridge. Recoil levels were approximately the same as the ever popular .30-06 yet the 7mm produced a much flatter trajectory and excellent down range terminal performance. In 1962, after much experimentation at the Bowman ranch, Remington released the 7mm Remington Magnum. Almost overnight it made several fine cartridges near obsolete, among them the .264 Winchester Magnum.
The 7mm Remington Magnum is currently one of the world’s popular medium game cartridges. It was also utilized by the U.S military as a sniper cartridge for specialized operations but has since been superseded by the dual purpose (anti personal/anti material) .338 Lapua and .50BMG cartridges.
The 7mm RM is available in a wide range of rifle configurations. Barrel lengths also differ from maker to maker. For many years, a common barrel length for sporting rifles was 24”. This is slightly too short for optimum performance, not only because of the 70fps reduction is velocity, but the shorter barrel raises both noise and recoil.
The 7mm Remington Magnum is definitely one of the most effective, versatile medium game cartridges available to hunters around the world. The two major complaints of its design are the short neck and belt. The short neck can sometimes effect bullet to bore alignment however this usually poses few problems and most hunters (hand loaders) never witness adverse effects. The belt is certainly an unfortunate accessory. It serves no purpose other than to make the cartridge ‘look’ like a magnum. The belt can cause feeding problems in rifles with already poor feed design. The remedy for this is correct insertion of cartridges into the rifle magazine. When a magazine is filled, it is important to ensure each case is pushed back as far as possible before placing another cartridge in the stack. With attention to practices, the belt soon becomes completely irrelevant and cycling is smooth and fast. It has been said that the belt helps thicken the primer pocket area and helps to maximize case life with warm hand loads. There is possibly a small amount of truth to this statement.
With 140 grain bullets, driven at velocities of between 3200 and 3300fps, the 7mm RM delivers extreme trauma on light bodied game out to ranges exceeding 400 yards. This bullet weight tends to lose its ability to produce wide wounding at ranges of around 650 yards. On heavily built medium game, the 140 grain bullet can produce somewhat less than ideal performance, wounding and penetration may be adequate but results can be erratic.
Loaded with 150-154 grain bullets driven between 3100 and 3200fps, the 7mm RM is devastating on a wide range of game out to ranges sometimes exceeding 900 yards. This bullet weight is more versatile than the lighter 140 grain weight but is still somewhat limited on large, heavy bodied medium game although wounding and penetration are more uniform. This bullet weight is best suited to game weighing less than 80kg (180lb).
The 160-180 grain bullet weights are the most versatile performers in the 7mm RM. Providing bullet construction is matched to the job at hand. The heavy weight 7mm projectiles can be used on the lightest of game through to animals weighing up to 320kg, producing fast clean killing out to 1000 yards. On game heavier than 320kg, the 7mm RM is capable of producing adequate penetration but not wide wounding relative to body weights. For this reason, if the 7mm is to be used on large heavy animals, neck and head shots are the most humane means of obtaining fast kills. For ordinary chest shots, the .30 caliber and medium bores provide much broader wounding through vital tissues.
The 7mmRM produces mild recoil in medium weight rifles with straight recoiling stock designs. In light weight rifles or rifles featuring Monte Carlo style stocks, felt recoil can be uncomfortable. It has been said that one of the goals of Remington in designing this cartridge was to duplicate the power and recoil levels of the .30-06 in order to ensure mainstream acceptance.
Unfortunately, the current trend towards light weight barrels does not help minimize recoil of the 7mm RM or any of the magnums. Factory rifles are available with either No.2 contour barrels (light sporter) or No.5 Contour (Varmint) as can be found on the Remington Sendero. No.3 and 4 contour medium weight barrels are found only on Sako rifles or through custom barrel makers. Barrel length is also a concern, several manufacturers continue to produce 24” barreled magnums while optimum barrel length is 26” for normal use through to 28” for open country hunters and long range enthusiasts.
The most suitable powders for reloading the 7mm RM are the slow burn rates IMR4831/H4831sc/N165/RL22 through to H1000/RL25. Hodgdon Retumbo (ADI2225) is a little too slow in most instances. Brass for the 7mm RM is readily available throughout the world and is produced by several manufacturers.
Hand loaded for a 24” barrel, maximum safe working velocities include 3250fps with 140 grain bullets, 3150fps with 150 grain bullets, 3100fps with 154 grain bullets, 3050fps with 160-162 grain bullets and 2900fps with 175 grain bullets and the 180 grain VLD.
From a 26” barrel, velocities include 3320fps with 140 grain bullets, 3220fps with 150 grain bullets, 3120fps with 160-162 grain bullets and 2950fps with 175-180 grain bullets. As always and regardless of barrel length, individual rifles will show preferences, some producing best accuracy at higher pressures, other rifles producing optimum accuracy with low pressure charges. As an example, some rifles will shoot the 162 grain bullets with optimum accuracy at an MV of 3040fps, some will give best accuracy right at 3120fps, others will give best accuracy at both pressure levels (sweet spots), producing relatively poor groups with intermediate charges. Experimentation is the key.
For dedicated long range hunters, best velocities are achieved with 28-30” barrels capable of pushing the 162 grain A-Max at 3200fps and the 180 grain VLD at 3000-3050fps. Optimum twist rate for all bullet weights in the 7mm RM is 1:9”.
Accuracy is of vital importance when working up a 7mm magnum load. Any gain in velocity over a standard cartridge will immediately be negated if the rifle will not shoot better than these cartridges at the extended ranges for which magnums excel at. This applies not only to long range hunters but also to the hunter who expects clean killing at 300 yards. Poorly bedded rifles or rifles set up with unreliable optics produce abysmal results in the field, slow killing gut shots being the most common result.
Personally, I believe that the 7mm Remington Magnum is one of the very best cartridges available for western hunters. The 7mm Rem Mag produces high power but at a recoil level that hunters can either tolerate or learn to tolerate. The 7mm Rem Mag is equally versatile in woods situations as it is at long range.
I often recommend the 7mm Rem Mag cartridge to clients and always state - “it’s a cartridge that never fails to please”. Nobody regrets buying a 7mm Remington Magnum, it can loaded fast, loaded for low recoil, loaded to produce minimum meat damage or loaded to produce maximum wounding for the fastest possible kills at extended ranges. The 7mm Rem Mag is not a good choice for less experienced shooters, best suited to intermediate experienced hunters. The 7mm Rem Mag is simple to work with and produces desirable results without the idiosyncrasies found in higher performance cartridge designs. The 7mm Rem Mag is essentially a headache free cartridge, a joy to shoot, a spectacular killer.
The 7mm Rem Mag is certainly not the most powerful 7mm. It also carries within its design, a degree of ignorance. The neck is short which can cause poor bullet to bore alignment when using hand loading dies of poor quality. The belt on the case head is absolutely pointless but it is there and there is nothing that can be done about it short of a complete re-design. Regardless of its theoretical flaws, this is an extremely efficient and effective medium game cartridge with little peer.
ABOUT THE AUTHOR
Nathan Foster has a long established background in the gun industry, recognized for his extensive research and for educating and supporting hunters around the world. Nathan has taken over 7500 head of game, testing the performance of a wide range of cartridges and projectiles, and is a worldwide expert in the field of terminal ballistics. His ongoing research has been carefully recorded, analyzed and documented in his online cartridge knowledge base for the benefit of all hunters and shooters (www.ballisticstudies.com). Rifle accurizing and long range shooting are among Nathan’s specialties. For many years, Nathan has provided both rifle accurizing services and a long range shooting school. Nathan is also the designer of MatchGrade bedding products and has assisted many 1000's of hunters worldwide to improve their rifle accuracy, shooting technique and hunting success.
Nathan Foster's The Practical Guide to Long Range Hunting Cartridges guides you through the process of choosing a cartridge and a projectile which suits you and your goals - step by step. This book, like many of Nathan’s books and writings, takes the approach that there is no need for you to be told which is the best cartridge for you - you can answer that question for yourself once you know how.
Instead the reader is taught the fundamental principles of long range game killing and is then given a methodical process for selecting the right cartridge based on their goals. The book looks at the various individual cartridge designs and the advantages and disadvantages of each cartridge so that the reader can then align their needs with an appropriate cartridge and projectile to get the job done.