Most the time Improved cylinder or cylinder choke is recommended for rifled slugs. I have seen lots of rifled slugs shot thru tighter chokes with no problems. What slugs did you buy? Does it say anything on your box of slugs? Many slugs have a note on the box about what choke they recommend. Remington Sluggers have a note that says "Choke & Trajectory Data: Rifled slugs may be fired through any choke; however, improved cylinder provides best results. These slugs will also perform well and fully rifled barrels and barrels fitted with rifled choke tubes."

I read that note many years ago and got an improved cylinder choke to replace my modified choke tube. My gun was dead on with the modified choke at 50 yards. It was about 1.5' low at 50 yards with the improved cylinder choke.

Since you have a smooth-bore shotgun with choke tubes, I am assuming you purchased rifled slugs and not sabots? If you purchased sabots you will probably need to get rifled choke tubes.

 

Theory is, the more open choke will be more accurate. Reality is, you need to shoot various slugs through the gun and chokes to find out.

My first slug gun was a 20 ga pump with fixed full choke. It shot Winchester "rifled" slugs very well but not Federal or Remington. I later found a barrel with screw in chokes where the Federals and Remington slugs shot adequately with the Improved Cylinder choke and poorly with the rest. The Winchester slugs were no better than the others but that fixed Full still shot them well. That fixed choke barrel was my slug gun for 20 years until I bought a rifled barrel for a different gun.

Forgot to mention, Federal Tru-Ball slugs have been at least adequate in the several guns I have used them in. They have not been the most accurate choice but they have all been accurate for as far as will shoot a standard slug.

 

Slugs may be in short supply, if you've not previously stocked up, so take with a grain of salt in that regard....

Take a few boxes and try with different chokes. See how they shoot.

My autoloaders and pump with smooth bores shoot well and accurately with mod. See how yours shoots with mod or IC. The pump also shoots well with a fixed choke slug barrel. All 12g. Good for hunting up to ~80y no problem. At least 2 loads shoot well for me in these guns: remmy sluggers and brenneke ko.

Just make sure which you use is working well, shooting accurately.

Personally I would stay with mod or wider. And I have. I never done full or tighter with slugs and wouldn't want too, and haven't needed to. So I can't speak to possible issues there.

Targets have been deer and wild hogs.

 

Attached is a very good video of what switching to rifled choke tubes did to the accuracy of a shotgun shooting slugs. It was unbelievably better with the rifled choke tube. Check it out and don't be put off by the good ole boy's accent. He does conduct a decent test.

 

thats an awesome group