Three gun set up help.

Last year I was given a Benelli Super 90 as a gift. With a 28in ribbed barrel I have no need for this gun in its current configuration as i already have an 870Mag for waterfowling and an O/U for upland hunting.

Someone please correct me if I am wrong, but this super 90 is basically and M4 for the civilian hunting market. and all parts should interchange.

Long story short, i would like to convert by Benelli for use in 3-gun. I have already found:
mag extensions
stocks
grips
charging handle extension

The only thing i can not find is the appropriate barrel and figuring out what i want to use for sights. Based on research Benelli only sells the 18.5 to LEA's or if you buy a complete M4. Anyone have any ideas as to where i can get a barrel (i have been watching gun broker for 3mo's and have not seen one)?

I am also going to need sights of some sort (i will be using irons for my local clubs regular 3 gun match). I am assuming any gunsmith can drill and tap my receiver for the rail/sight configuration found on other M4's.

Please give me any advice you may have on this shotty, will this be a good 3-gun set up? Anyone have an aftermarket sight they are fond of?

The Super 90 is an M1, not an M4. That's the good news, as it's probably half the weight. The bad news is that a new barrel will cost you about $450, and yes, Virginia, you can get an 18.5" barrel.

Be ready to spend just under $100 for the mag tube, $175 for the stock and grip, and $50ish for the charging handle. To be honest, you're better off selling that one and buying a used M1 Tactical on Gunbroker for $500 or so.

The good news is that Nordic Components makes about everything you need to get your Benelli ready for 3gun. (http://www.cactustactical.com/osc/shotgun-accessories-c-412_458.html)

The other good news is that an 18.5" barrel isn't an absolute necessity. A 20" or 21" barrel will work just as well in almost all cases.

The bad news is that you're going to most likely have to order the barrel straight from Benelli, and they're going to charge you out the wazzoo for the privilege of buying their product.

Regarding after-market sights, I'm a fan of the ones offered by Hi Viz. (http://www.hivizsights.com/) Specifically the triangular inserts seem to work well, as they give you a decent way to gauge holdover for engaging longer-range slug targets.