The 6.5-300 Weatherby Magnum

By Chuck Hawks

Weatherby introduced their new 6.5-300 Magnum cartridge, the biggest and fastest 6.5mm commercial cartridge in the world, in 2016. The parent .300 Weatherby case is based on the full length .300 H&H Magnum case blown out to increase powder capacity and given the trademark Weatherby double radius shoulder. In other words, it is a big case for a .30 caliber bullet and a very big case for a .264 bullet.

The standard (.30-06) length .264 Winchester Belted Magnum has always been considered overbore and a barrel burner and the recent (2014) .26 Nosler, based on a Remington Ultra Mag case shortened to .30-06 length and necked-down, has greater case capacity (approximately 96 grains of water) than the .264. The 6.5-300 Weatherby, which requires a long magnum action, is even bigger than the .26 Nosler, holding approximately 105 grains of water. Draw you own conclusions.

Weatherby offers the 6.5-300 Magnum only in rifles using their Mark V action, which is known for its smoothness and great strength. Weatherby 6.5-300 Mark V rifles come with the famous Weatherby style Monte Carlo stock and a 26", 1-8" RH twist barrel. (Except for the 6.75 pound Ultra Lightweight, which is supplied with a 28" barrel.) For 2017, the 6.5-300 is being offered in the Mark V Deluxe, AccuMark, Ultra Lightweight, WeatherMark, Terramark, Outfitter and Arroyo models.

Weatherby factory loads for the 6.5-300 include a 127 grain Barnes LRX bullet at a muzzle velocity (MV) / Muzzle Energy (ME) of 3531 fps / 3516 ft. lbs., a 130 grain Swift Scirocco bullet at 3476 fps / 3487 ft. lbs., and a 140 grain Swift A-Frame bullet at 3395 fps / 3583 ft. lbs. These ballistics were determined in a 26" test barrel. All three Weatherby 6.5-300 factory loads carry a 2017 MSRP of $98 for a box of 20 cartridges.

Since 140 grains is the most useful bullet weight in almost all 6.5mm hunting cartridges, let's examine this Weatherby factory load's ballistics in more detail. The sectional density of a 140 grain 6.5mm bullet is .287 and the ballistic coefficient of the 140 grain A-Frame bullet is .401.

Velocity: 3395 fps MV, 3122 fps at 100 yards, 2866 fps at 200 yards, 2624 fps at 300 yards, 2394 fps at 400 yards, 2176 fps at 500 yards

Energy: 3583 ft. lbs. ME, 3030 ft. lbs. at 100 yards, 2552 ft. lbs. at 200 yards, 2139 ft. lbs. at 300 yards, 1781 ft. lbs. at 400 yards, 1472 ft. lbs. at 500 yards

Here is the trajectory of that load, computed for a scoped rifle with a line of sight 1.5 inches above the bore centerline and a 300 yard zero.

Trajectory: -1.5" at muzzle, +2.8" at 100 yards, +3.5" at 200 yards, 0" at 300 yards, -8.6" at 400 yards, -23.3" at 500 yards

The 6.5-300 Wby. Mag. is intended to be an ultra-long range cartridge for hunting medium game (Class 2) animals, critters weighing less than about 300 pounds. However, I have no doubt that, with proper bullet placement, the 140 grain A-Frame bullet would also put down elk and other Class 3 animals.

After more than 120 years of service around the world, 6.5mm has recently become a glamor caliber in North America. As regular Guns and Shooting Online readers know, I have long been a fan of the caliber and I have written many articles extolling the virtues of 6.5mm cartridges, particularly the sensible and competent 6.5x55 SE and .260 Remington. These rather mild cartridges will kill anything the 6.5-300 can kill, but the 6.5-300 can do it from farther away. For those very few hunters who are good enough shots to take advantage of its flat trajectory, the 6.5-300 Weatherby Magnum is everything for which you could ask.

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Copyright 2016 by Chuck Hawks. All rights reserved.