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Visaman
December 6, 2009, 10:08 PM
I dont know mutch about the design of cartridges.
I have come up with the following design, just for fun.


.666 Devil

Bullet diameter .666 in (16.916mm)

Neck diameter 0.712 (18.1mm)
Shoulder diameter 0.748 in (19mm)
Base diameter .904 in (20.4 mm)
Rim diameter .904 in (20.4 mm)
Case length 5.91 in (150.114 mm)
bullet weight: 900grain (58 g) TMJ

It would be fun to have a cartridge that has that kind of name.

Applications :
ultra long range big game metallic silhouette ( cape buffalo and elephant sized plates ? ).

Is it plausible ?
What about chamber pressure, bullet velocity and energy ?
It is obvious that it needs a large muzzle brake an a sturdy bi-pod.
It will need a rifle weighting 49.5 kg (109 lb).

Jim Watson
December 6, 2009, 11:04 PM
Well, you have kind of split the difference between a .50BMG and a 20mm.
I would estimate a reasonable load for your little fantasy would generate 55000 psi as is usual for brass cased cartridge rifles, and get that 900 grain bullet up to 3000 fps.

The main real world use for such a round would be military anti-materiel sniping at a range of perhaps two miles. I see no sportsmanlike hunting use for a hundred pound ultra long range rifle.

It would not be readily availble in the USA because anything over .50 is considered a Destructive Device unless shown to have innocuous "sporting purpose" like an elephant gun. Doubt a heavy caliber high velocity long range rifle would pass the examination.

Sodbuster
December 6, 2009, 11:19 PM
Run it by Barrett. ;)

mapsjanhere
December 6, 2009, 11:21 PM
That thing would try to give the JDJ series a run for its money. Good luck on the BAFT negotiations, and on finding a 150 mm long case, that's longer than your standard 20 mm rounds.

fisherman66
December 6, 2009, 11:22 PM
If Jim's calculations are correct it would have a little recoil. The name seems apropo on that count alone.

How's about a 6x66 instead? Might be a barrel burner.

James K
December 6, 2009, 11:46 PM
I don't know if you could legally make the cartridge, but if you make the gun you will need the special OK for manufacture of a destructive device, and of course each customer would also have to get BATFE approval and pay the tax. And it could be sold only through DD dealers, who are rare birds.

I agree that .666 Devil would be a neat name, but it would be best to keep the cartridge on paper.

Jim

Visaman
December 7, 2009, 06:53 AM
Sadly, it is nonlegal to acquire firearms that has a bullet diameter over 0.467 here in Norway.

Here is a ballistic table for that round, sightet in at 500 feet.
bullet coef: 0.567


Range Velocity Impact Drop ToF Energy Drift
0 3000 -0.5 0 0 17987 0
100 2827 9.53 2.22 0.11 15972 0
200 2665 15.18 8.81 0.21 14194 0
300 2509 15.91 20. 0.33 12581 0
400 2359 11.09 37.4 0.45 11121 0
500 2215 0 60.74 0.59 9805 0
600 2075 -18.21 91. 0.73 8605 0
700 1941 -44.5 129.73 0.87 7529 0
800 1813 -80.04 177.52 1.03 6569 0
900 1691 -126.16 235.88 1.21 5715 0
1000 1576 -184.41 306.38 1.39 4964 0

Recoil energy calculation;

Bullet weight in grains 600
Velocity in fps 3000
Powder charge in grains 300 ( the 20x72RB uses 400 grains of IMR 4831 smokeless powder to propel a 2000-grain (130-gram) projectile at 2800 feet (850 meters) per second. 50 BMG 248.0 gr H50BMG 3,029 fps, 655 grains bullet. )
Weight of firearm in lbs 100
Recoil Impulse in (lbs sec) 13.31
Velocity of recoiling firearm (fps) 4.29
Free recoil energy in (ft/lbs) 28.52