what the poster above says is true, you could theoretically shoot a foster type slug NOT SABOT through a full choke barrel, some actually shoot better that way. However, this is not recommended for most, higher barrel presures basically. Foster type slugs are made smaller on purpose to accomodate different choke sizes. If youve ever taken a look at a foster type slug while not encassed in a shell, they basically look like a tennis ball cut in half with rifling on the outside, I.E. easily compressible. Do not fret if you dont have a cylinder choke, you should be able to shoot successfully through the whole gamit, however i probably wouldnt shoot them through an old beater with a full choke.
have at it, happy shooting