If you are referring to that choke, as one of the Rem-chokes that came with the gun, assuming it was supplied with the typical three choke assortment, ic, mod, full.
ABSOLUTELY DO NOT SHOOT anything through that barrel without a choke tube screwed into it!
For slugs, typically cylinder or improved cylinder is the tube to be used, if you do not have a rifled slug barrel.
You can always purchase a rifled slug barrel for your gun, it should even come with sights. Probably cost around a $175-$200.
The internal threads at the end of your barrel will be damaged if fired without a choke tube installed, DON'T DO IT!
Keep your eyes peeled for cock(birds)
Keep your shots above your shoulders!