A little less than a year ago, i decided to buy a shotgun.  Stupid me went to wal-mart and got the only black one they had--a remington 870 express 3.5" w/ 26" barrel.  It now has <100 rounds through it.
I now want to have a tactical shotgun w/ 18" barrel, mag extention, copstock, etc.

If you were in my shoes, would you build up the 3.5"?  The main disadvantage is the longer slide throw.  BTW, i've seen 3.5" supermag barrels go for $140.

Thanks

Dude,

Imagine a 3.5" mag touched off with a cop stock.

Are you a masochist?

Deersniper, There are some awesome buckshot rounds made in 3 1/2". 18 pellets of 00 buck is offered by all of the big three. Federal offers 24 pellets of #1 buck and Winchester offers 54 pellets of #4 buck. Three good reasons to use the 3 1/2" receiver if you can stand the recoil. MIKE.

Does anyone know where i can find a 3.5" chambered, 18" barrel?  Can the chamber be lengthened?

I expect that a 3" 870 barrel could be rechambered to 3.5".   According to Remington's web site 2 .75" and 3" 870 barrels will fit on the 3.5" (Super Magnum) gun.

www.remington.com/firearms/xtrabbl.htm

NOTE: Model 870 Extra Barrels with 2-3/4" chambers will fit Super Magnum, Magnum, and 2-3/4" receivers.

NOTE: Model 870 Extra Barrels with 3" chambers will fit Super Magnum, Magnum, and 2-3/4" receivers.  These barrels will handle both 2-3/4" and 3" shells when used on Magnum receivers.  Use only 2-3/4" shells when these barrels are used on 2-3/4" receivers.