I'm under the impression that in order to put a choke on a barrel, it must be threaded for chokes.  I have an 870P IMP CYL 18" bbl.  I assume this does not come with a barrel threaded for chokes.  Am I correct?

Can I add a choke to this myself, or do I need to send it out and have it done?  I'm a little confused now.

What are you trying to do?  What do you want to accomplish?  You will have to send it out to be done.

Why spend money to add a choke tighter than IC to an 18" barrel?  Short barrels are not that great for longer shots.  I have an 1100 that has a 21" vent rib with choke tubes.  It is in many ways a great all around gun, especially when I am handling my dog or I am in thick cover.

If you want to make your gun more versatile, like dual role defense and hunting, buy a second barrel from 23" to 28".  Since you are a newbie to shotguns a longer barrel will be better for learning to be a good shot, like a 26" and up.

Again, what do you want to do

Thanks for the replies.

Ok.. You ask what I want to do?  I'm just trying to figure out how to make my SG more accurate at longer ranges.  I'm not looking for rifle accuracy, just some more than what it's capable of doing now.

Also, I'm not looking for cheaper and easier.  I don't mind spending a few extra bucks.  But I don't want to go with a longer barrel b/c it's primarily an HD gun.  I'm not being closed minded about buying another barrel.  I could possibly still go that route.  I was just thinking if there was a way I could do it without changing my existing 18" configuration, I'd consider trying that.

Would a poly choke be a good or bad option?

Is there any 'good' option for achieving what I'm trying to accomplish?

Quoted: Is there any 'good' option for achieving what I'm trying to accomplish?

You already have it.  A lot of people find that IC over plain cylinder is a little more accurate.  In terms of being more accurate in home defense....................practice.  End of story.  Your gun is capable of doing a lot now, the X factor is you, the shooter.  Ignore some of the crap you may have read, just go launch slugs from it and see for yourself.  A big bead is all you need.

If you want better accuracy in the field, longer barrel with a vent rib.

I friggin' hate poly chokes.  Funny thing is I think they seem to be making some kind of come back?  At least in this forum.  I think most people who hunted or shot in the 60's and 70's do NOT own those things now.  You won't see one in my home.