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Old October 11, 2005, 09:47 PM   #26
Dave Haven
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The .50 BMG has been necked-down to .338. The late, great Skip Talbot did it. The ".338-.50 Talbot" is listed in the latest edition of Cartridges of the World. Muzzle velocity is 3700 FPS with a 250 grain bullet. Barrel life is rather short, due to throat erosion. Imagine that.

The .378 Weatherby has been necked-up to .458. In 1946, IIRC. Can you say, ".460 Weatherby?"

One of the most interesting cartridges I've seen (that actually shoots) is the "Fat Mac .50" Developed by the late, great Gale McMillan. It's the 20mm Vulcan cartridge shortened and necked-down to .510. Gale described it as "sort of a .50 PPC" It will shoot a 750 grain bullet at 3500 FPS. That's over 20,000 foot-pounds of muzzle energy.
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Old October 11, 2005, 11:23 PM   #27
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I've got a wildcat that's a little extreme. Its a .357mag pistol brass necked down to .17. A real short, fat mag. Its not that hot a round. The .17 Rem has higher velocities. But its quite accurate, and the rifle is a dream--a Martini Cadet which is about the size and weight of a Red Ryder BB gun. But it shoots sub-MOA at 200 yards, when there's not much wind. At 100 yards, wind almost doesn't matter.

I didn't invent it, I inherited it from the original owner. But its fun having something no one else has.
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Old October 11, 2005, 11:39 PM   #28
Mike Irwin
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"There's a 357mag necked down to 25 called the 25WinMag, IIRC."

It's actually called the .256 Winchester Magnum, and was a production cartridge for a number of years. Marlin chambered one of their lever guns for it, and the Ruger Hawkeye single shot was made for a number of years.
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Old October 11, 2005, 11:47 PM   #29
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.950 JDJ, a 20mm vulcan case necked down to .950. It fires a 3600 grain projectile at 2200 fps. SSK made a few out of mcmillan rifles and krieger barrels. Each rifle weighed 110 pounds. Taylor notes that it is "not for the financially challenged or faint of heart". Equally silly is the .729 Jongmans firing a 1048 solid copper projectile at 2265 FPS. The gun weighed 21 pounds, used 340 grains of powder. Taylor notes recoil is "brutal". No thanks!
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Old October 12, 2005, 08:06 AM   #30
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14,000 FPS huh?

I don't know what to say to that, besides I must have one
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Old October 12, 2005, 08:20 AM   #31
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How about taking a 300 Rem Ultra case, size it down to 30-06 length to fit standard long action rifles, keep the angles on the shoulder, blow the neck to 338 and presto a standard length beltless 338 mag that will put the 338 win mag to shame. Or was that done by Dakota as their 338 Dakota round? josh
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Old October 12, 2005, 09:24 AM   #32
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There's already a 338-06, which is a 30-06 blown out to .338. Better ballistics than the 35Whelen, but slightly less energy.

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Old October 12, 2005, 10:36 AM   #33
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Yup the .330 Dakota is 06 length. The .338 Rem Ultra Mag is 3.55 OAL. Both are badasses, not very Goofy though.
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Old October 12, 2005, 10:44 AM   #34
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A few years ago I read something, can't remember where, that stated that the fastest a bullet can be driven using conventional smokeless powders is about 5,800 or 6,000 fps. It has to do with how fast the pressure wave will propagate, or something like that.
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Old October 12, 2005, 10:53 AM   #35
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Yes Mike I read the same article...

I believe it was referrering to the misnotion that Weatherby had. He was talking about how fast he was going to push his new stuff. A scientist in the field. Said nope won't happen.

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Old October 12, 2005, 10:58 AM   #36
roy reali
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Weak Link

Actually the weak link in firearms is the case. Do you realize that Savage has taken a step towards this problem? They have that muzzle loader that can use smokeless powder. If you could eliminate the brass case, the strenght of the rifle's chamber will be the new pressure limiter.
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Old October 12, 2005, 05:31 PM   #37
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What is the fastest velocity a non self propelled projectile ever attained? I've read 4200 fps from 22 swifts firing 40 grain projectiles. Has anyone personally reached 5000 fps yet without blowing up bullets? I've done 4000+ with my 22-250 and I experienced grey streaks (not in my shorts) before with a weird noise coming from the bullets breaking up in flight. josh
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Old October 12, 2005, 06:40 PM   #38
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Quote:
If you could eliminate the brass case, the strenght of the rifle's chamber will be the new pressure limiter.
I believe the military tried some guns like that. Without the casing the weight savings were amazing and soldiers could carry so much more ammo, but the problem was the ejected case takes a lot of heat away from the gun. So with no case to eject the guns liked overheating.
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Old October 12, 2005, 06:59 PM   #39
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caseless ammo

Yeah, and since you don't have to worry about ejecting the spent case, an automatic weapon can have extremely high cyclic rates of fire (ala G11).

I would wager the highest velocity out of a "gun" was obtained with this scenario...

http://nuclearweaponarchive.org/Usa/Tests/Brownlee.html

I think the estimate was ~56km/s...or 183,727 feet/s; I would wager that it didn't go far....
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Old October 12, 2005, 08:35 PM   #40
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^^ Dang. That's a fairly large caseless gun. It's got a real low cyclic rate though.
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Old October 12, 2005, 10:19 PM   #41
Dave Haven
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The modern 120mm tank guns use a combustible case which is essentially part of the powder charge. They fire a saboted fin-stabilized projectile through a smoothbore barrel. The projectile weighs several pounds, and muzzle velocity is 5700 fps.

In WWI, the Germans built the "Paris Kanon". It was a 210mm (rifled) cannon with a muzzle velocity of 5280 fps. Range was 80 miles.
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Old October 13, 2005, 01:02 AM   #42
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Don't forget the 22-250. It's the ultimate "Lets cram this full of powder and see what happens" round.

/BTW, 22-250 + 40 grains of IMR-4320 + 55 grain bullet = Case failure.
//Learned the hard way.
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Old October 13, 2005, 11:59 PM   #43
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950 JDJ, a 20mm vulcan case necked down to .950
Or would that be necked up to .950? 20MM = .787cal
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Old October 14, 2005, 09:56 PM   #44
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Oops, quite right ...I should have thought a bot harder about the conversion. There is a good write up on this cartridge in "Cartridges of the world".
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Old October 15, 2005, 11:27 AM   #45
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joshua, Phil Sharpe's "Complete Guide to Handloading", 1952 edition, showed a Frankford Arsenal "gun" that was said to have propelled a ten-grain projectile at some 10,000 feet per second. (I'm working from memory; I'm some 1,400 miles away from the book.)

The device--the "barrel"--resembled an 8" diameter cylinder with the very small hole through it. A view of the breech wasn't shown.

Art
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Old October 15, 2005, 01:08 PM   #46
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How 'bout the 7.62mm X 39 Russian necked up to .358? It would kill same as parent cartridge out to 150 yards or so but the load development and machining costs would be fun. Sort of.
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Old October 15, 2005, 01:34 PM   #47
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How 'bout the 7.62mm X 39 Russian necked up to .358?
The Russians did this (9mm) for a silenced military cartridge. http://world.guns.ru/ammo/sp-e.htm I also read that someone did a similar version and had a Mini-30 adapted for it.
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Old October 15, 2005, 01:44 PM   #48
Death from Afar
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I vaguely recall reading smething about German hyper velocity shooters as well, and it was something about how 5000 fps was about the maximum for a rifled small arms projectile. Something about how the projectile rips to pieces due to excess torque. Does that sound right?
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Old October 15, 2005, 02:10 PM   #49
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Mike read the same thing I did.

The limit isn't bullet construction. Early .220 Swift bullets tended to explode enroute to their targets until bullets were redesigned to handle the stresses.

One limit is the expansion of gunpowder gases. The expansion wave front tops out at 5500-6000fps, so a different means of pushing the bullet has to be used to get past that hurdle.
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Old October 15, 2005, 02:38 PM   #50
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Which is why MBT rounds use discarding sabot ammo?
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