.550 Magnum

Tuesday, August 27th, 2019

.550 Magnum

Developed by Neal Shirley in 2003 the .550 Magnum become a unique phenomenon in big bore calibers. This dangerous game cartridge has gained a lot of traction with hunters from around the world. Taking game at close range is typical for most hunters as taking them at distance is no different than hunting plains game. When Shirley developed this round, he had several requirements in mind. He wanted a low chamber pressure design as opposed to a high pressure cartridge. High pressure rounds tend to stick in a chamber, especially in the hot African sun.

Several loads were developed using a 700 gain .550” dia. bullet propelling it at 2,150 fps with 7,200 ft.-lbs. of energy. Another load was developed using the propelling the same bullet at 2,300 fps with 8,222 ft.-lbs. of energy. The recoil on these loads is not quite as severe as one might think. It is said the recoil is much like that of a .458 rather than that of a .550 caliber. This is attributed to the stock design, rifle weight and the low pressure chamber.

Niel Shirley has a letter from the ATF exempting this rifle/cartridge from the over .50 caliber rule and list it as a sporting gun.

Roberson Cartridge Company is a custom manufacture of Vintage, Obsolete, Hard to Find and Wildcat calibers.

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