For 2016, Weatherby introduced their new 6.5-300 Magnum cartridge, the biggest and fastest 6.5mm commercial cartridge in the world. As the name implies, this is a .300 Weatherby Magnum case necked-down to accept 6.5mm (.264") bullets.

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 and is more of the same.

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 in the full magnum length version of their 9-lug Mark V action. This fine action is known for its smoothness and great strength. As far as I know, it was the first commercial action with a bolt diameter the same as the locking lug diameter, a feature intended to minimize bolt wobble when the action is operated. It uses three rows of front locking lugs spaced to provide a 54-degree bolt lift, still the shortest in the industry.

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 for a reason I cannot fathom is supplied with a 28" barrel.) The Weatherby stock does a good job of controlling recoil, which is a Very Good Thing, given the powder capacity of the 6.5-300 case and the very high velocity claimed for Weatherby factory loads.

For 2017, the 6.5-300 is being offered in the Mark V Deluxe, AccuMark, Ultra Lightweight, Terramark, Outfitter, Arroyo and the RC (Range Certified) versions of the preceding models. Excepting the Deluxe, which is stocked in fine walnut, all of these rifles are supplied with hand-laminated composite stocks.

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 2016 MSRP of $98 for a box of 20 cartridges.

For comparison, the muzzle energy of the 140 grain 6.5-300 bullet is 156 ft. lbs. more than the muzzle energy of the same weight bullet from the standard length .270 Weatherby Magnum cartridge. As the range increases this energy advantage decreases and I doubt any animal could live on the difference in killing power between the two.

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

Based on these figures, the 6.5-300 Wby. Magnum is clearly a powerful, flat shooting cartridge. However, the Weatherby 140 grain factory loads for the .270 Wby. Mag. actually shoot slightly fatter than the new 6.5mm-300 and hit harder beyond 200 yards, due to the superior BC of their Nosler AccuBond (.496) and Ballistic Tip (.456) bullets.

The .270/140 grain Ballistic Tip load drops 22.6 inches at 500 yards when zeroed at 300 yards and the .270/140 grain AccuBond bullet drops only 21.6 inches. Perhaps Weatherby should offer a 6.5-300 load using the 140 grain AccuBond bullet (BC .509), which would give the 6.5-300 a slight ballistic advantage over the .270 Wby.

The 6.5-300 Wby. Mag. is intended to be an ultra-long range cartridge for hunting medium game (Class 2) animals, such as feral hogs, deer, antelope, sheep, goats, black bear, caribou and similar animals 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 bull elk and other Class 3 animals. The less powerful .264 Win. Mag. has been successfully doing so since the mid-1950's.

As a hunting cartridge, the long 6.5-300 Weatherby Magnum has little practical advantage over the standard length .270 Weatherby Magnum, which kicks less. Indeed, the latter can be had in the same Weatherby Mark V rifles, as well as several other Mark V models.

However, after over 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 versions. For those hunters who are relatively new 6.5mm fans and who wish to own the latest and fastest, the 6.5-300 Weatherby Magnum is everything you could ask for, presented in rifles of superior quality and performance.