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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