How much?Zero.
If you had asked me how many thousands of rounds of ammo I fired in 2009...
BATF knows whether you believe there are no registries or not. The records are never destroyed, and if you did something, they can and would go search and find any you ever bought, from their archives. Its not a registry by definition ofcourse, but who cares, it is what it is, and can serve similar purposes if need be.I aint telling nobody and since there's no gun registration, nobody needs to know. I might have bought one and had it stolen before I got home, therefore no paper trail.