I just got a Stoeger Coach gun and it has the fixed chokes. I read where they were Imp cyl and modified.
What would be a good slug to use with this gun?
You can shoot any slugs through your gun. Brenneke are quite good slugs, however you should try several brands of "rifled slugs" to see which your gun likes best. There is frequently no rhyme or reason as to ahy a particular gun shoots a particular brand/type of slug best. When you find the one your gun "likes" keep using it.