A gun that started out as a pistol CAN be made into a rifle, and back into a pistol, legally.  BUT, the configurations must both be legal.  In order to make a pistol into an SBR, you must apply for a tax stamp on a Form 1 and complete the NFA process just like any other gun; having started with a pistol doesn't make you exempt from NFA laws.

Free-floating your barrel probably makes it LESS prone to damage, but if you're dropping them out of planes, I don't think it matters.

Before you go too far on the SBR, you might want to read this: [url]www.ammo-oracle.com[/url]

-Troy