Buried in Title 27,Prt 479 Definitions is this:
Note the last two exemptions in the definition of 'Destructive Device'...
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Destructive device. (a) Any explosive, incendiary, or poison gas (1)
bomb, (2) grenade, (3) rocket having a propellent charge of more than 4
ounces, (4) missile having an explosive or incendiary charge of more
than one-quarter ounce, (5) mine, or (6) similar device; (b) any type of
weapon by whatever name known which will, or which may be readily
converted to, expel a projectile by the action of an explosive or other
propellant, the barrel or barrels of which have a bore of more than one-
half inch in diameter, except a shotgun or shotgun shell which the
Director finds is generally recognized as particularly suitable for
sporting purposes; and (c) any combination of parts either designed or
intended for use in converting any device into a destructive device as
described in paragraphs (a) and (b) of this definition and from which a
destructive device may be readily assembled. The term shall not include
any device which is neither designed or redesigned for use as a weapon;
any device, although originally designed for use as a weapon, which is
redesigned for use as a signaling, pyrotechnic, line throwing, safety,
or similar device; surplus ordnance sold, loaned, or given by the
Secretary of the Army under 10 U.S.C. 4684(2), 4685, or 4686, or any
device which the Director finds is not likely to be used as a weapon, or
is an antique or is a rifle which the owner intends to use solely for
sporting purposes.
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"...soley for sporting purpose" is the key.
There have been several commercial and wildcat rounds made/chambered in the over .50cal catagory. The firearms have been sporting arms and there has been no problem.
The parent cases have been non-military as the general consensus is that they don't like the idea of a blown out 50BMG or other large military round. But the makers usually run their plans past the BATF before investing any time & $ into their projects to avoid a problem or disappointment.
The 600Nitro and the 700nitro are a couple of the commercial offerings in the last few years that come to mind.
The 577Snyder though it has a military background, that was mainly in what is now 'antique status firearms' that would not come under the Fed control/concern anyway. So that military usage background may not be of a concern,,if indeed it is of a consideration at all.
The caliber and some other commercial 577's variations were chambered in many sporting arms later, so it does have that 'sporting' history for sure. I'm sure you wouldn't be the first to do such a project, but I'd still check w/ BATF Technologies Branch first for the OK.
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A pure sporting round is the 577 Nitro Express/3inch. You might consider that one too.
Here's some loading data to get you started!
But are you sure you want to shoot 600 and 700gr bullets under approx 100gr of your favorite powder in a HandiGun?
http://www.accuratereloading.com/577ne.html
Good luck with your project,,have fun!
