Snowflakes in Hell has a posting (via Ry Jones) about a converter kit to turn a Ruger 10-22 rifle into a pistol.

I'm not utterly sure of the benefit (why not just buy a Ruger pistol?) but I'd agree that the legal risks are considerable. ATF's position is that the receiver is the gun, and a rifle receiver is thus a rifle, so one turned into a pistol becomes a short-barreled rifle. The Thompson Center case suggests this may not be right, but I wouldn't consider it 100% on point, and when a violation is a felony, I'd like more assurance than that.