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The US government purchased MK 248 MOD 1 .300 Winchester Magnum match-grade ammunition in 2009 for use in adapted M24 Sniper Weapon Systems and other .300 Winchester Magnum sniper rifles like the US Navy Mk.13s. This ammunition was developed as a .300 Winchester Magnum Match Product Improvement (PIP) and uses the 14.26 g (220 gr) Sierra MatchKing Hollow Point Boat Tail (HPBT) very-low-drag bullet fired at a nominal muzzle velocity of 869 m/s (2,850 ft/s) ± 15.2 m/s (50 ft/s). According to the US Navy this ammunition should increase the maximum effective range of .300 Winchester Magnum sniper rifle systems to 1,370 m (1,500 yd),
However, the short neck with the shoulder moved forward does cause some real problems. Since the .300 Winchester Magnum is designed to work out of a standard length action heavier bullets will need to be seated deeper into the case. Since many heavier .30 caliber (7.62 mm) bullets have a long taper, and these bullets will be required to be seated deeper into the case, the neck will end up being positioned in the ogive rather than on the shank of the bullet due to the fact that Winchester had moved the shoulder forward. This prevents the case from having a good grip on the bullet. Under recoil such loosely held bullets in the magazine will be pushed back into the case. Also, if using a highly compressed load the cartridge might “grow” in length and may not be able to fit into the magazine. For these reasons bullets weighing over 200 gr (13 g) are not recommended. Norma goes further recommending that bullets heavier than 180 gr (12 g) not be used with the cartridge