The 338 Lapua Magnum is one of the better known .338″ diameter cartridges on the market today. While it may not have a particularly large following in the hunting community, the military/LE/tactical community are enamored with it. Its widespread military acceptance makes for great PE and because of this, the non-hunting shooter is most likely more aware of it than any one of the other terrific .338″ cartridges. But what about the other .338s? One of my favorites is the 340 Weatherby Magnum.
Of the .338″ diameter cartridges in the hunting rifle world, the 338 Winchester Magnum is probably best known. It has two semi popular smaller cousins, the 338 Federal (.308 Winchester necked up to .338″) and 338-06 (30-06 Springfield necked up to .338″) which are better known now then they once were. Once you get into the big 338s, you have some other cartridges that are very similar. The 338 Lapua has a case capacity of 114.2 gr of water, while the 340 Weatherby- 98.0 gr, 338 Remington Ultra Mag- 113 gr., and the capacity of 338-378 Weatherby is 125 gr. I’ve sent hundreds of rounds of 340 Weatherby down range and was enamored with the cartridge in the late 90s.
Like other Weatherby cartridges, the 340 was a belted magnum with a unique, radiused, double venturi shoulder. The belted design may look dated today, but the first time I saw it, it seemed like the perfect cartridge.
When I wrote my 338 Lapua barrel length post, I couldn’t help but wonder why more people weren’t making more 338 Lapua comparisons to my old favorite, the 340 Weatherby. They were after all, remarkably similar. Here is my quote from that passage:
I don’t understand why the 340 Weatherby (above, left) isn’t compared more to the 338 Lapua Magnum (above, right), especially with the 250 grain class bullets. True, the 338 Lapua holds around 15 grains more water, but they both push a 250 grain bullet at similar speeds. Factory specs on a 250 grain bullet from a 26″ 338 Lapua are 2,950 feet/second. My 340 Weatherby shot a 250 grain bullet 2,948 feet/second all day long. When the Lapua started gaining traction in the US, I kept asking guys why they just didn’t shoot a 340.
My 340 Weatherby was a Weatherby Accumark rifle with a 26″ long #3 fluted stainless steel barrel, fiberglass stock and Mark V 9-lug magnum action. Take a look at the images below that I took nearly twenty years ago!
I can’t remember exactly why I bought that gun, or that cartridge, but I vividly remember it battering me off the bench. 
A quick trip to “Old Bob”, the local smith, and I ended with with a 25 1/4″ barrel and a custom blended muzzle brake. The brake did the trick. It was still punishing to shoot for a long session but the brake did an excellent job of bringing recoil down to a manageable level. You should also note the Scotchbrite kitchen-pad finish to reduce the reflective properties of the polished stainless steel barrel. That was high tech back in the day!
I ended up settling on a 250 gr. bullet over RL-22 for a muzzle velocity of 2,998 feet/second. The gun hammered, 3-shot (it’s a hunting rifle, not a match rifle) 1/2 MOA groups were the norm. Brass, while expensive, had an impressive service life. One set of casings had 12 firings on it! I attribute this to a couple of factors, good brass and I didn’t full-length size. I would use RCBS full length dies, but I would back them off so only about 2/3 of the neck was formed.
I ended up taking it on a plains game hunt with a 2.5-8 Steiner scope in Talley mounts. Shortly before I left for my hunt, I headed to the range to confirm my zero, the target is below:
Once I landed, I confirmed zero yet again at the air strip, and everything stayed where it was supposed too. My 340 Weatherby performed well on game from the diminutive Duiker at a full sprint, to a Nyala walking across a hill a few hundred yards away.
If you get a chance to get your hands on a 340 Weatherby, give it a shot!
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