Mike, you do not want to shoot without a choke tube in the barrel, you could damage the threads. That being said, you may want to change the choke tube, especially if you have a full or extra full choke installed. Conventional wisdom says rifled slugs shoot best with improved cylinder choke tube. Ammunition is highly variable, and all guns digest ammunition a little differently than one another, so start with IC and if that works stick with it. Generally you want to shoot slugs through the most open choke possible. This will make them more accurate as the tighter chokes can cause them to deform and not fly straight......Also on pg 49 of your owners manual, it states "Only improved cylinder and cylinder choke tubes are recommended for slugs. Anything tighter than these choke tubes may cause damage and/ or injury if a slug is fired through the barrel." ... Have a great day!

Mike, the screw in chokes will be fine as far as the Cylinder/Improved Cylinder and Modified Chokes. You can fire slugs with the full choke but the best accuracy is attained with the Improved Cylinder Choke. Cheers and stay safe!