My grandfather left me a Remington 11-87SP a while back. He always told me that it was a Sabot rifled barrel and healways used sabot slugs in the gun. After a wet Michigan opener, I decided to really clean and oil the gun as this is the first time I carried the gun. Upon inspection, the barrel is a 21" smooth bore barrel with a rifled choke and rifle sights.Not a rifled barrel. Obviously this gives me more optionsandchances to use the gunifI purchase different chokes. I realize all guns like and dislike different ammo and I need to get to the range to test, but what type of accuracy and distance can you generally excpect with a rifled choke vs a rifled barrel?

Thanks in advance for the information.

We could guess all we want and we'd still be no closer to knowing exactly the truth for YOUR particular barrel/choke tube/slug. The ONLY way of knowing for sure is to shoot different slugs from a bench and find out how they group.

This is absolutely correct.

However, as a general rule, a rifled barrel will shoot better than a rifled choke tube, because the slug gets started with a spin and does not need to get started spinning after slamming into the rifled part at nearly muzzle velocities. Some rifled choke tubes have been exceptionally accurate, and some have been just the opposite.

try the federal true ball slugs in your smooth bore. you might be surprised.

All above are true. I shot 5 different brands of rifled slugs through my 21" 870 smooth bore and found the Federal Tru-ball to be the most accurate.
As for the difference between a rifled barrel and a rifled choke. IMO I think a rifled barrel is more accurate than a smooth bore with a rifled choke. Especially with saboted slugs. I just can't imagine how about 3" of rifling (rifled choke) can initiate enough spin on a slug as it is leaving the barrel around 1100 fps.
I was contimplating getting a rifled choke. Let me know how you make out.

I saw a tv show a long time ago, and they did some super slow-motion photography of a sabot slug exiting a gun with a rifled choke tube. It was spinning to beat the band. Their conclusion was the tube is "almost as good" as a fully rifled barrel.

I'm sure your grandfather shot sabots if he told you that's what the gun shot best.