The .275 H&H Belted Magnum
By Chuck Hawks
This interesting cartridge was the first of the 7mm Magnum cartridges, the ancient forerunner of today's popular 7mm Remington Magnum. Perhaps I should mention that ".275" is the bore diameter traditionally used by the British to describe the caliber known as "7mm" in Europe and the U.S.
The prestigious old gun making firm of Holland & Holland has always been creative, and they have had a tendency to push the envelope in terms of cartridge design and development. They are not the staid, conservative sort of firm one thinks of as typically British. So much for stereotypes.
So it is not as surprising as it may initially seem that it was Holland & Holland who originated the concept of the belted magnum cartridge. The belt was added to a rimless case to allow positive headspacing even in the absence of a sharp shoulder, while still allowing the cartridges to feed smoothly from the box magazines of repeating rifles.
Their .400/375 Belted Nitro Express was the world's first belted cartridge, but not a magnum. It was followed in 1912 by the .275 and .375 Belted Rimless Magnums, the first magnum cartridges. No doubt the experts at H&H felt that you could pretty much hunt anything in the world if you had a flat shooting 7mm rifle and a powerful .375 medium bore rifle. You still can.
In 1925 Holland and Holland expanded their magnum line by introducing their .300 Belted Rimless Magnum, which subsequently sired a host of .300 Magnum cartridges. The .244 Magnum appeared in 1955, and the latest H&H Magnums are the .400 and .465, introduced in 2003. All of these H&H magnum cartridges are covered in articles on the Rifle Cartridge Page.
In 1912 smokeless powders were not what they are now. The British were using long stick Cordite powder, which was inserted into the case before it was necked down. That partially explains the considerable body taper of the early H&H Magnum cases. Cordite burns very hot and is hard on barrels, which limited the performance attainable even in a large case such as the .275. With the modern powders available to reloaders the .275 H&H is approximately equal to the 7mm Remington and 7mm Weatherby Magnums in performance. They are, after all, based on the same basic .375 H&H case shortened to about 2 1/2 inches in length.
Following typical British and European practice, there was also a rimmed, rather than belted, version of the .275 Magnum, intended for use in single shot and double rifles rather than repeating rifles. This was known as the .275 Flanged Magnum. Its case capacity is identical to the .275 Belted, but it was usually loaded to somewhat lower pressure.
The .275 Belted Magnum case is 2.50" long with a standard magnum rim diameter of .532". The diameter just forward of the belt is .513" and the diameter at the rather sharp shoulder is .454". This means that the case has a lot more body taper than modern magnums. The neck had an outside diameter of .325" and accepted .287" diameter bullets. (Note: some sources call for .284" bullets.) Cartridge overall length is 3.42", which means that long bullets do not need to be seated as deep in the case as with modern 7mm Magnum cartridges.
The .275 Belted was factory loaded by Kynoch and Eley in the UK and Western Cartridge in North America. Bullets ranging from 105 to 180 grains have been offered, including the common 140, 160, and 175 grain weights. The Western factory load was discontinued in 1939, on the eve of World War II.
Original British factory loads gave a 140 grain bullet a muzzle velocity (MV) of 2650 fps and a 160 grain bullet a MV of 2700 fps. The Western factory load used a 175 grain bullet at a MV of 2680 fps and muzzle energy of 2810 ft. lbs. These loads seem pretty tame by modern standards because they were limited by the lack of suitable powders.
According to P.O. Ackley (as quoted in the 9th Edition of Cartridges of the World), a 160 grain bullet can be driven to a MV of 3050 and ME of 3305 ft. lbs. by 59.0 grains of IMR 4350 powder. That is more like it! At 200 yards the remaining velocity of that load should be about 2658 fps and the remaining energy 2509 ft. lbs.
The trajectory of that load, computed for the modern 160 grain Nosler Partition 7mm bullet (BC .475, SD .283) looks like this: +2.5" at 100 yards, +3" at 150 yards, +2.3" at 200 yards, +0.3" at 250 yards, -2.9" at 300 yards, and - 7.6" at 350 yards. The maximum point blank range (+/- 3") is 301 yards.
Such a load would do for all of the world's thin-skinned game. As a "light" rifle for an African Safari, the .275 H&H would be an excellent choice, just as Holland & Holland intended. Except for the powders poured into them, the capability of 7mm Magnum cartridges has really not changed much since 1912.
Copyright 2004, 2012 by Chuck Hawks. All rights reserved.