The .450 Watts Magnum

By Chuck Hawks

.45 Magnum cartridge
Illustration courtesy of Hornady Mfg. Co.

The wildcat .450 Watts Magnum is a .45 caliber safari cartridge based on the .375 H&H Magnum case necked-up to accept .458" bullets. Ballistically, the .450 Watts Magnum is virtually identical to the later .458 Lott, and the two look very similar. However, the .450 Watts and .458 Lott cartridges are not interchangeable.

The .458 Winchester Magnum is also based on the .375 H&H case, but shortened to work in a standard (.30-06 length) bolt action rifle. The Watts cartridge requires rifles with a long (.375 H&H length) "magnum" action.

Because the .458 Winchester Magnum is essentially a shortened version of the longer .450 Watts, .458 Win. Mag. cartridges can ordinarily safely be fired in .450 Watts rifles. (Since the .450 Watts is a wildcat and not a standardized caliber, this may not be true of all .450 Watts rifles and chambers.)

According the fine reference book Cartridges of the World by Frank C. Barnes, the wildcat .450 Watts was designed by a pair of Yakima Washington residents named Watts and Anderson. This was sometime around 1950. Jack O'Connor took a .450 Watts rifle to Africa on one of his safaris, and mentioned it in print.

The .450 Watts is based on a belted, straight walled case. The nominal dimensions include a rim diameter of .530 inch, a base diameter of .513 inch, a neck diameter of .481 inch, and a case length of 2.85 inches. This is about .35 inch longer than the .458 Win. Mag. case and allows the .450 Watts somewhat greater powder capacity than Winchester's .458 Magnum. The cartridge overall length is 3.65 inches. The standard rifling twist for Watts rifles is 1 turn in 14 inches.

P. O. Ackley's loading data for the .450 Watts shows a 400 grain bullet propelled by 85.0 grains of IMR 4198 powder at a muzzle velocity (MV) of 2670 fps with muzzle energy (ME) of 6320 ft. lbs. A 500 grain bullet can be driven to a MV of 2500 fps and ME of 6920 ft. lbs. by 98.0 grains of IMR 4320 powder. These are very heavy (maximum) loads with velocities close to those attained by the .460 Weatherby Magnum. More typical .450 Watts loads drive a 500 grain bullet at a MV of about 2300 fps and ME of 5872 ft. lbs, giving about a 200 fps advantage over the .458 Win. Mag.

The "Rifle Trajectory Table" shows that, from a scoped rifle, a 500 grain bullet at a MV of 2300 fps has a maximum point blank range (+/- 3 inches) of 219 yards when zeroed to hit 2.9 inches high at 100 yards and 1 inch low at 200 yards.

Recoil is always an important consideration, and never more so than when dealing with elephant rifle cartridges. None of these big bore bruisers are easy on the shoulder, and the .450 Watts is truly violent. In a 10 pound rifle firing a 500 grain bullet at a MV of 2300 fps it generates about 70 ft. lbs. of recoil energy. The recoil velocity of that 10 pound rifle is in excess of 21 fps, so don't believe the stories about a "slow, heavy push." What you feel is a fast, heavy slam, analogous to being hit in the shoulder with a 10-pound sledgehammer moving 21 fps.

On the other hand, the effectiveness of the .450 Watts cannot be denied. It will drop an elephant in its tracks with a well placed bullet. The African hunters who have used the .450 Watts Magnum on game such as elephant, rhino, and buffalo are usually very pleased with its performance.

The .450 Watts had a run of popularity until the introduction of the .458 Winchester Magnum in 1956. The .458 Win. became the African elephant cartridge of choice and was picked-up by most rifle and ammunition manufacturers. After that the .450 Watts faded into obscurity.

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Copyright 2003, 2012 by Chuck Hawks. All rights reserved.