February 04, 2025
By Brad Fitzpatrick
Roy Weatherby was the king of fast cartridges, and he was an instrumental player in the magnum craze of the mid-20th century. Weatherby began designing cartridges in the 1940s, but it wasn’t until 1968 that he took aim at the 6mm market.
Heretofore Weatherby had based his hyper-velocity cartridges on the .375 H&H Mag., shortening, necking down and applying his signature Venturi shoulder. But for the .240 Wby. Mag., introduced in 1968, he designed a unique case. It looked very Weatherby with its belt and rounded shoulder, but the rim diameter was 0.473 inch, and case length was reasonably close to a .30-06, so the new .240 Wby. Mag. could fit in a .30-06-length action.
The .243 Win. and 6mm Rem. Mag., both released in 1955, had beat the .240 Wby. to market by more than a decade. However, the .240 bested the velocity of both cartridges by at least 300 fps. Winchester’s .243 Win. Super Short Mag. threatened the Weatherby’s velocity record for a while, but that cartridge has largely disappeared, leaving the .240 Wby. to lead in 6mm speed.
Modern ballistics science shined a light on high bullet ballistic coefficients—rather than sheer speed—as the way to shoot farther, with Hornady ’s 6.5 Creedmoor leading the charge. It wasn’t long before shooters began toying with the 6.5 Creedmoor, and Outdoor Life editor John Snow and George Gardner of GA Precision worked to neck down a 6.5 Creedmoor to 6mm, and the 6mm Creedmoor was born. While it started life as a target cartridge, hunters—myself included—found it to be an excellent performer on game.
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Differences (Info provided by the author) Aside from their bullet and case rim diameters, the .240 Wby. and 6mm Creedmoor have little in common. The 1.92-inch Creedmoor case lacks a belt, has a 30-degree shoulder, and the chamber is designed with virtually no freebore. Weatherby’s case measures 2.5 inches long, features a radiused shoulder and a belt, and chambers have substantial freebore.
Most 6mm Creedmoor rifle barrels feature twist rates between 1:7 and 1:8 to stabilize bullets that may weigh up to 115 grains, whereas the Weatherby features an older 1:10 twist.
The Creedmoor will push an 80-grain bullet up to 3,400 fps, but the cartridge was truly envisioned for higher BC bullets of 95 to 105 grains to be pushed 3,000 and 3,200 fps. A .240 Wby. will propel an 80-grain bullet upwards of 3,500 fps, and Weatherby factory ammo includes 72-grain bullets at 3,700 fps and a 100-grain load at 3,275.
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Let’s compare two popular loads side by side: Weatherby’s 80-grain Barnes TTSX at 3,440 fps and Hornady’s 103-grain ELD-X Precision Hunter at 3,050 fps. When sighted in at 100 yards, the Weatherby has 1.8 inches less drop at 300 yards than the Creedmoor and almost five inches less drop than the Creedmoor at 600 yards. At about 800 yards, though, the Creedmoor’s high BC bullet shoots 1.4 inches flatter than the Weatherby, and at 1,000 the Creedmoor drops almost 30 inches less than the Weatherby.
Versatility Department Wind drift dramatically favors the 6mm Creedmoor’s higher BC bullet, too. At 800 yards, the .240 Wby. load drifts more than 68 inches in a 10-mph crosswind compared to 45 inches for the Creedmoor.
There are lots more ammunition and rifle options for the 6mm Creedmoor, including some less expensive ones. You can get ammo for about $2 per round. Weatherby is the sole provider of rifles and ammunition for the .240 among major brands, with ammo prices starting at around $3.75 a round.
The 6mm Creedmoor, clearly, is more versatile, but for hunters who like the Weatherby’s laser-flat trajectory out to about a quarter-mile, that round is still as versatile and deadly as it was in 1968.