There is a big enough difference between the two that firing an AI case in a Gibbs chamber is likely to cause the case to rupture or split.
To safely fireform cases for the Gibbs, you need to size the neck with a larger caliber die to create a "false shoulder" for the case to headspace against during the fireforming process. I have also heard of people seating the bullets long enough to jam in the rifling to accomplish the same thing.