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Discussion Starter #1
Listen up. I've had a brilliant idea. Again.

The .505 Gibbs is a powerful big bore cartridge. I've seen data for the Gibbs that impresses me greatly. How about a 600 grain bullet propelled by 120 grains of Reloder 15 at 2300 fps?

Now suppose one were to neck the Gibbs up to .510. And then suppose one seated the Hornady 750 grain AMAX. We would have a bullet with a ballistics coefficient of over 1.00.

Now it would be quite possible to load this combination to 2200 fps. Now let's stop for a minute.

This round would have more kinetic energy at 500 meters than a .338 Lapua Magnum has at the muzzle. And at 1000 meters it has the power of a .300 Magnum at the muzzle. And at 1500 meters the 12.7x80 mm would have the power of a 6.5x55mm at the muzzle.

The 12.7x80 would have a velocity of about 1470 fps at 1000 meters and a velocity of about 1200 fps at 1500 meters.

A 12.7x80mm could be built on a CZ-550 action. Now imagine this:

Mike Rescigno builds the rifle using a CZ-550 and a Krieger barrel together with a MacMillan stock. The rifle would be called the F-80. And it would feature a 24 inch barrel.

The rifle would weigh about 20 pounds and it would be carried on a biathlon sling.


Fluffy
 

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Hmmm you have something.

But why not step up to a 26-30 inch barrel. That little bit of barrel length would give tht much more vel. and energy at the 1000-1500 yard range.

Tom
 

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Discussion Starter #5
The recoil would be managable from a 20 pound rifle.

And this is a .50 that could be built from an off the shelf action. Brownells sells CZ actions for slightly more than 500 bucks.

You would not need a special oversize action as you would need with the .50BMG

The 12.7x80 would use far less powder than the .50 BMG and it would be far cheaper to use.

And Norma makes brass for the parent .505 Gibbs case. It would be very easy to form brass. And this .50 will deliver the goods at 1500 meters. You don't need to have a .50 BMG. It's overkill.

And the barrel does not have to be longer than 24 or 25 inches. 2200 fps is easily in reach with just a 24 inch barrel. With the fantastic ballistics coefficient of the .50 you don't need every last foot per second.

The idea is to have a relatively portable .50. And this .50 would be legal for use in Kommiefornia.

Another thing to consider is that the parent .505 Gibbs was designed for use in tropical heat. The case was oversized and designed to operate at a chamber pressure of 46,000 cup. Now if you increase the pressure just a bit, you can easily reach 2200 fps with a 750 grain bullet.

In my mind I want a rifle that is a scaled up version of the F-51. I want a relatively short stiff barrel in a man-portable rifle.

In case there are further murmurs from the peanut gallery, I would point out that the CZ-550 is avaiable in .505 Gibbs and this stock rifle weighs 9.9 pounds. If we double the weight of the rifle, I say that the recoil of the 12.7x80 would be managable in a 20 pound rifle.

And the rifle could be carried on a biathlon sling. The rifle would be worn like a backpack.

Fluffy
 

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Discussion Starter #6
I just did a few calculations. From a 20 pound rifle the free recoil energy of a 12.7x 80 would be 74 foot pounds.

From a 25 pound rifle, the free recoil energy of the 12.7x80 would be 60 foot pounds.

By way of comparison, the free recoil energy of a 31 pound Barrett .50 BMG is 97 foot pounds.


Fluffy
 

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I fired up Quickload and ran some numbers just for fun...

There are 17 powders that would get you 2200f/s from a 24 inch barrel using much lower pressures than RL15.

Seating the bullet to only a half inch shank depth is necessary to keep the pressure to a manageable level. Even the best powder with the lowest pressure that will get that velocity is running at 51,000psi and the 505 Gibbs brass is only designed for 39,000psi. I don't think brass life will be very good... :D

The recoil would be equivalent to shooting a 460 Weatherby Magum with a 500 grain bullet at 2550f/s out of a 14 pound rifle. :!:

Not my idea of fun... :D
 

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Discussion Starter #10
I stand by my numbers. In a 20 pound rifle, the 12.7x80mm would have a free recoil energy of 74 foot pounds. This represents 25% less free recoil energy than a .50 BMG fired in a Barrett Light Fifty.

In a 25 pound rifle, the 12.7x80mm would have a free recoil energy of 60 foot pounds. This is 40% less free recoil energy than a .50 BMG fired in a Barrett Light Fifty.

Finally, modern cartridge brass is more than strong enough to handle pressures over 51,000 psi. These pressure levels are routine for many, many calibers. And don't forget, I would be using Norma brass. Norma simply makes better brass than Remchester.


Fluffy
 

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You know, I don't often disagree with cats. Then again, most matters 'tween kittehs and I are not up for discussion.

FluffyTheCat said:
Finally, modern cartridge brass is more than strong enough to handle pressures over 51,000 psi. These pressure levels are routine for many, many calibers. And don't forget, I would be using Norma brass. Norma simply makes better brass than Remchester.
No doubt about Norma being better...but that doesn't make the web of the case thicker for a given design Fluffy. Heck, dead-soft brass is strong enough to contain 100,00psi....if it's 12 inches thick. You see my point? It's not all about how good or bad an alloy is, or how close tolerances a manufacturer holds: it's about the basic case design. If the SAAMI sez the design is rated to 39,000, and you try to push that almost 25% higher (and probably without any piezometers on the barrel anyway, right?)...well dang, seems to me like you're really cutting a LONG way into the safety factor of those ratings.

You can stand behind your numbers because it's your lives (or eyes) to waste fuzzy...I'll be behind the nearest large oak.

-Nate
 

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Nat

Would this idea work however with a different alloy then? If so, what would the alloy be? I think the brass is the least of the issue here as any material fitting the performance criteria could be used - lets assume that isn't a scenario for mass production and cost of cartridge creation was irrelevant.

How about the idea of the round though? Would not such a round have a superior performance characteristic that would enable greater accuracy and 'issue resolution' at impact over very long distances?

Cheers
 

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Discussion Starter #14
Oi vey.

I come up with a brilliant idea and now I am covered with peanut shells.

First they said that the recoil would kill me. Now after I dispel this goofy notion, now the brass is going to kill me.

Before I do anything, I would consult with Norma to find out exactly how strong their brass is. I bet it is strong enough. But if it is not, then it can be strengthened.

Do you remember how the .416 Rigby case served as the parent case for the .338 Lapua? The Lapua company recognized a good idea when they saw it and they built proper brass.

Now where would we be if the developers of the .338 Lapua were discouraged by those who toss peanut shells?

I still say that I have something here. And with the help of our Finnish friend Reine, we will contact Lapua and see what it would take for them to make 12.7x80 brass.


Fluffy
 

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FluffyTheCat said:
Oi vey.

I come up with a brilliant idea and now I am covered with peanut shells.
:D :D

First they said that the recoil would kill me. Now after I dispel this goofy notion, now the brass is going to kill me.
I never said your numbers were in error. Or that the brass would kill you. I did say it wasn't designed for that amount of pressure.

Before I do anything, I would consult with Norma to find out exactly how strong their brass is. I bet it is strong enough. But if it is not, then it can be strengthened.
The Rigby case wasn't strong enough and it was built for higher pressure than the Gibbs. Lapua took the 416 Rigby case and shortened it by almost 3/8th of an inch, redesigned the case interior and changed the alloy and heat treatment to allow it to run at a significantly higher pressure.

Do you remember how the .416 Rigby case served as the parent case for the .338 Lapua? The Lapua company recognized a good idea when they saw it and they built proper brass.
It'll probably take an order of about 1/4 million cases to make it worth their while. That was what it took for one gunsmith I knew to get his case up and running.

Now where would we be if the developers of the .338 Lapua were discouraged by those who toss peanut shells?
Not intended to discourage you just to point out some areas that might need a little developement.

I still say that I have something here. And with the help of our Finnish friend Reine, we will contact Lapua and see what it would take for them to make 12.7x80 brass.


Fluffy
Never said you didn't and I hope it works out. :wink:
 

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Now Fluffy, when you are calculating the recoil of the .50bmg, is the program your using to calculate it accounting for the significant recoil reduction from the muzzle brake? I've shot a barret .50, and it felt more like a shotgun, just with more shove, and a kick in the face as well, in fact, I recently finally got to shoot a .300WM in a 8.5lbs rifle, and I believe it kicked more than the .50, and as a plus it didn't slap you in the face either.

I can see a bmg creating 97ft/lbs of recoil from a 31lbs right with no brake, but not with a brake.

Branden
 
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