Smooth Bore - Full Choke and Slugs

Itialian Sport and Ulysses are right on. You won't hurt a gun by firing a slug through full choke. However, it won't be as accurate. Here's why:

Like they said- the slug is smaller diameter than the barrel. As the propellant burns, the expanding gasses leak past the riefled slug. As they do, since the slug is rifled the gasses impart a spin on the slug, like wind through a windmill. On an IC or open choked gun, the diameter of the barrel stays more consistenly opened, so the gasses pass more consistently, and the slug spins nicely. On a full choke gun, as the slug nears the end the barrel constricts, speeding up the gasses passing the slug and accelerating the spins, however since the gasses are no longer as consistent flowing past the slug, the spin can be affected, and the slug loses accuracy.

The slug gets it's spin in the barrel- not necessarily from the air it passes on the way to the target.

Ahh yes- the wad. However, if on a smoothbore the slug either:
A. gets it spin from the air, or
B. gets it's spin from the barrel,

How can a guy get such tight groups for a smoothbore gun? The variables (mainly the air) could vary enough that it seems to me there would be lots of inconsistency.

I guess I had some misinformation from years past- I was told that slug wads allowed some gass to pass by. I never got great accuracy from my smoothbore- hence the rifled barrels I now use. Thanks for the correction guys.