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Old June 14, 2019, 06:51 AM   #1
stagpanther
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Radial/screw in bolt locking

Interesting that today's GunsAmerica digest shows two new versions of bolt locking schemas that use "screw in" movement--one by the Army (enabling the peak psi to ramp up to 100 k psi) and one by CMMG that increases lock timing and thereby reducing blowback pressure and carrier mass used in a pistol cartridge AR. Look great--when things go right--but my devious mind always ponders "what if" when things don't go so well.

https://www.gunsamerica.com/digest/u...y-machine-gun/

https://www.gunsamerica.com/digest/b...bine-in-40-sw/
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Old June 14, 2019, 08:39 AM   #2
Jim Watson
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I wonder what turns the screw bolt in the Army high pressure gun.
I wish they had shown the screw bolt and chamber collet in the same drawing.
Maybe we will get some more detail if they pursue it.
F.W. Mann had the "Hamburg Gun" with interrupted thread locking lugs. It had none of what he called "backleash" and we call "head clearance" because "the bolt screws right up to the head of the cartridge."
There were a number of puff pieces about a military super duper 6.8mm with ballistics about like a .270 Weatherby. Maybe this screw breech would make it feasible.

I had read about the CMMG design. Looks like it would be very dependent on lubrication of the lugs. OMG, the Blish Lock returns.
It is said to moderate recoil. This might let PCC shooters use PCP ammunition instead of loading down for the 16" barrel.
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Old June 14, 2019, 09:24 PM   #3
stagpanther
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The collet/screwbolt looks like it "self headspaces."
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Old June 15, 2019, 05:31 AM   #4
Mobuck
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Generally speaking those sort of designs don't handle handle dirt, grit, or fouling well.
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Old June 15, 2019, 06:55 AM   #5
BBarn
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Interesting design. Since the firing forces against the bolt face tend to want to unlock the breech, I would expect to see wear on the spiraled surfaces and the hex. But that's probably an acceptable trade off to gain a substantial increase in permissible chamber pressure.
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Old June 15, 2019, 01:08 PM   #6
kozak6
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Very interesting.

That collet is pretty wacky. It's kind of like a floating chamber, probably to help prevent case-head separation.

This sort of thing has been tinkered with since the dawn of self loading firearms, so I don't really see it suddenly working out now. Neither Mannlicher, Thompson, nor Kalashnikov had much success with this sort of thing either.
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Old June 15, 2019, 05:40 PM   #7
stagpanther
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Quote:
Generally speaking those sort of designs don't handle handle dirt, grit, or fouling well.
That was my first thought--but since the Army's developing it I assume high reliability in a hostile environment would be a must.
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Old June 15, 2019, 06:51 PM   #8
Jim Watson
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Project for high chief-to-Indian ratio pentagoners and sweetheart contractors.
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