Ok maybe this question will get some responses.  I've got the 24" deer hunting smooth barrel.  I have not done alot of testing yet on accuracy (i'm planning on doing more) but it has shown some good accuracy in the past with brenneke slugs.  My question is I saw on the mossberg website, if you go under the sights section, they show you can get a 18.5 barrel, with the orange front sight post and the ghost ring sight.  Couple of questions if anyone knows,  I suppose I should be asking them this, but here goes:

Is this option accurate, or can it be with slugs?  Or for that matter buckshot or any other shot?  

It says that the reciever has to be drilled and tapped for the ghost ring?  My receiver is already drilled and tapped for scope mounts, Is that what they're talking about or does it need other holes?  

My main goal for this shotgun is Deerhunting, Coyote or small game hunting, and self defense.  

Am I just better off with the extra velocity with the 24" barrel?  I don't know much about shotguns, it's all new to me.  I'm getting into it more because of certain areas I may be hunting are requiring either a shotgun, muzzleloader or pistol.  Out of all my guns this is my best option.  I don't have any longer barreled revolvers or a muzzleloader.  And I'm getting the shotgun bug now.  Plus, this sight is great but does anyone have another sight that talks about this kind of stuff where there is more interest in hunting and self defense shotguns?

That 18.5 with the ghost sights seems like it would be cool.  

Velocity is not going to change enough to matter. Accuracy is not dependent on barrel length. You could just cut the barrel back and maybe get chokes installed if you want a shorter barrel.Buckshot ussually like a little choke any way. You can buy the sights seperate the mounting holes may work or you could use a red dot or low powered scope.

See, now you've just raised more questions.  I've heard that a good choke would be a good thing.  But It doesn't look like the shorter barrels come with it.  I'll have to check that again.    Can I add a choke to the one I have now???  Ooohh my head is spinning.  Wanna know something weird.  In our state from june to december, no buckshot is allowed.  So If I'm going to shoot coyotes the largest I can use is bb.  I figure it'll still work at close enough range but it's a stupid rule.  I'm sure the bb would be better with a choke too, eh?  Then I could use it as a turkey gun if I ever go.  

A good smith can cut the barrel and add screw in chokes.If your not set on a short barrel I would just buy one with screw ins already.Sell your 24" to offset it deer season coming and for some reason shotgunners always wait till 2 days before to buy a deer barrel.

I have the 18.5" with ghost ring sights and it works great.  Dead on (point of aim) at 50 yards and I can keep slugs on the target at 100 yards. I would recommend that barrel.
I sent the barrel to Vang Comp and had it ported and back bored, it will keep 00 buck groups around 7-8"s at 25 yards. (just for info). and you really can tell the difference with the recoil.

what is back bored?  Thank you for the response, everyone.   How much is your slug dropping at 100 yards?  And which slugs do you use?

I went to a gun show last night and a guy there had a 590 with the extended mag tuge and the ghost sights.  SWEEEEEEEEEEET.  That sight is niiiiiiice.  The factory one. I don't know if I'll get it because I actually like the open sights I got on my barrel and I'm used to them but that sight is fast and easy to see.  With both eyes open as well.  It's almost like looking through a red dot sight but even easier and quicker if you ask me!!!!!!!!!!!!!!!!!!!  It's very tempting.