http://www.weaponsguild.com/forum/index.php?topic=42867.0

Retrieved: 12/06/2013


TRX
August 16, 2013

Adam Hall's spy novels are notorious for mangling anything gun-related, from plain WTF? to "you've got to be kidding." He apparently made things up as he went along.

In 1965 he wrote "The Quiller Memorandum", which wasn't as bad, gun-wise, as some of his other stuff. Guns don't appear much in the book, with one notable exception:

[snip]

"The bullet from a small 8 mm. short-trigger Pelmann and Rosenthal Mk. IV spins in the region of two thousand revolutions per second"

"In the case of Schrader the skull had shattered badly and only one side of his face was recognisable."

[/snip]

That's all we're given, which considering Hall's gun knowledge, it probably plenty...

As usual, the Voices wanted to know what a "short trigger" (like, WTF?) Pelmann and Rosenthal 8mm might be, if it was real. Bouncing up and down on the flexible limb of pure speculation, it would likely be a revolver. Other than notable exceptions like the Luger and Mauser, the Germans weren't much into locked-breech autoloaders, and an 8mm as powerful as described wouldn't likely be in a blowback pistol.

So, we might be looking at a revolver. There's a simple solution here - according to my "Guns of the World", several German manufacturers made revolvers of S&W design, copies or licensed. The Germans did have a few unique revolver designs, but other than cheap .22s and .32s for export, they didn't seem to like revolvers much.

Okay, we have this 8mm that's so powerful it can blow up a human head like a pumpkin. That's asking a lot even for a .44, so we'll just figure up the most powerful 8mm that could reasonably be expected, pre-1965.

Something like the .327 Federal didn't exist then, but there's no reason it couldn't have been made. But for "more power", you'd possibly be looking at a necked-down .357 or .44 Magnum. And in 1960-1965, such things were of interest, in America anyway, with the .22 Jet and .357/44 Bain & Davis. A .357 necked down to 8mm looked good for a first-pass design.

Hmm, I seem to remember that there were some problems with tapered or bottlenecked cases in revolvers. So I hit Google...

Oh, my. "Asps. Very dangerous. You go first!" You might as well pick any hot button subject and throw a troll-bomb in.

So, leaving that whole jihad to become a feature of the next Internet Special Olympics, let's assume case setback is real. What might be done about it?

The cylinder of a revolver has a .003-.010 gap at the front so it will clear the barrel. There's a similar gap at the back, to accomodate varying rim thicknesses and occasional stuck cases. I, er, had a few problems along that line once, back when I was trying to get every bit of velocity I could out of the .357 cartridge. Managed not to blow anything up, so I'll count that as a win.

Anyway, the cylinder has to have some clearance, and it floats a few thousandths. What if we could change the clearance to zero when firing, then opening the clearance up afterward so it can rotate? If there's no clearance, there's no cartridge setback. And we only need a few thousandths.

What I've been sketching is variants on a moveable breechblock. One type is like a falling block, sliding up and down at an angle to wedge the cylinder. The other is a round breechblock with the sprung firing pin in it, moved forward and back via a cam.

Most of the designs I've sketched would work, but they depend on lots of small, fiddly bits made to close tolerances. They would undoubtedly bring joy to the Germanic heart, but I've been trying to work up something simple and elegant.

Does the world *need* an 8mm magnum revolver with a moveable breechblock? Even just as a thought exercise? Obviously not, but that's not the point...


TRX
August 16, 2013

Could you use gas from firing to force a floating chamber within the cylinder forward?

Possibly, but your cylinder OD would go up.

As a variant of your idea, how about bleeding off some gas just ahead of the case mouth and pressurizing the cylinder axis pin, forcing the cylinder against the back of the frame?


TRX
August 17, 2013

Bring on the sketches!

By the way, one advantage of the Nagant system is that since the cylinder pilots on the back of the barrel, you have positive location of the cylinder to the barrel. No slack from clearances for the latch and its slots, no indexing errors. Thus, the forcing cone goes away, which means no distortion of the bullet as it passes that area. Note the Soviets used variants of the Nagant successfully in Olympic shooting contests.


TRX
August 18, 2013

That too, but since we were discussing something hypothetically German, "difficult to machine" would almost be a given...

I'm wondering if there's enough spring in the case so that, if a light spring or plunger pushes it all the way forward against the cylinder when it's fired, it might spring back enough to get the couple of thousanths we'd need to rotate the cylinder. PO Ackley claimed that with a straight case and sharp shoulder, the case would lock itself into the chamber while under pressure, but would spring back and extract freely, unlike the older highly-tapered designs.

On the other hand, in my experimental days I managed to stick a few .357 cases... "too much of a good thing", you know.


TRX
August 21, 2013

An interesting article on stress in rifle actions, with mention of how radial case expansion reduces bolt thrust:

Steel Support for the Brass Cartridge Case.pdf

Go back up to "thewellguidedbullet.com" for some other interesting stuff.