.340 Deathray

Lee Martin · Feb 13, 2013

I was digging through my reloading bench and ran across this abomination:

After my dad built his first 50 BMG in 1991 we thought about making it a switch barrel. Being unaware of Skip Talbot’s work with necked BMGs we designed the “340 Deathray”. It’s basically a 50 BMG squeezed to 338 and improved to 25 degrees (this iteration isn’t fire-formed). We built reamers and dies but never the gun.

Sometime around 1994 I read about Skip’s experience with his 338 Talbot and that sand-bagged the project. 177.0 grains of 8700 could be safely ignited behind a 250 gr bullet but charge density was low. 77% to be exact. That combination only returned 3,700 fps from a 44” barrel. In an attempt to bolster charge density he cut the case by an inch. Like its bigger brethren the smaller Talbot topped out at 3,700 fps. By comparison a 340 Weatherby can hit 2,600 fps with a 250 gr. The 338-378 and 338 Lapua can do 2,800 – 2,900 fps with half as much powder and a much shorter package. Diminishing returns on steroids, right?

We may resurrect this thing just for giggles. Surplus powders along with commercial grades like US 869 may be fun behind a Barnes banded solid. 4,000 fps would be a stretch but it'd be neat trying to get there.

Anyways, I thought some of you’d get a kick out of this. I’ll keep you guys posted if we proceed.

gasbag · Feb 13, 2013

That is a sexy cartridge.
You could be a sniper in Colorado and have your target in Wyoming with that thing. :mrgreen:

gunman42782 · Feb 13, 2013

That would give the .338 Lapua a run for it's money for sure!

ChiefMuzz · Feb 13, 2013

Deathray?

What made you come up with that name Lee? :wink:

David Bradshaw · Feb 14, 2013

Lee.... looks like a scaled-up .17/.220 Swift. Suppose a bit of throat erosion?

Possible, however, necking the .50 SPOTTER to .338/.50 Spotter would make the .338 SPOTTER. The .50 Spotter is to the .50 BMG what the .308 is to the .30-06. There might be available powders to turn the .338 Spotter with 300 grain bullet into the .338 Mighty Might.

A look at Hodgdon data for .338 with listed max velocity only from 250 grain bullets. No barrel lengths provided.

338 Ruger Compact Mag----250 SFT AF/SS----55.5/H414 (760)=2453 fps.
338 Win Mag----250 HDY SP----67.5/H4350=2657 fps.
340 Weatherby----250 Sierra SBT----83/H4831=2784 fps.
338 Lapua----250 HDY SP----108/US 869=2879 fps.
338 RUM----250 HDY SP----101/Retumbo=2964 fps.
338-.378 Weatherby----115/Retumbo=3072.

My SAKO L61 .338 Win Mag (24", 1:10") launches the Sierra 250 BTS over 70 gr./IMR 4350 at 2780 fps. Sierra seated to just kiss rifling in .375 H&H action. This load is too long for .30-06 length magazine. Note another L61 .338 WM tolerates 67/IMR 4350----three grains less.

Point is, barrel length is a critical component of overbore cartridges. A look at the .378 Weatherby, also from Hodgdon:

378 Weatherby----270 HDY SP----115/H4831=3102 fps.
378 Weatherby----300 Nosler Partition----100/H4350=2940 fps.

Tells me what we've proved across the valley; the .378 Weatherby is a sleeper. Now, how about the .378 SPOTTER? Or just a .378 Weatherby with 40" to 48" barrel? A take-down falling block, ala Jon Powers .50 BMG, but with scope on barrel, and jam nut fit for a pipe wrench?

Of all the non-military cartridges listed above, I consider the .338 Win Mag and .378 Weatherby the best balanced. (Who says this thread is about balance?)
David Bradshaw

Lee Martin · Feb 14, 2013

I agree David. I'd never consider building one of these with less than 44" worth of tube. 20mm surplus powders may also be on option as you recommended.

Ultimately, your 338 Spotter idea is a better design. We may go that route in time but since I already have reamers and dies for the Deathray, that'll come first.

Oh, and someone asked about the name. Around the time we drew this thing up I watched a B-Horror movie from the 50's. Can't remember which one but the aliens had a "deathray". Thought it sounded cool so I tagged our 340 as such.