Watch Ebay for a rifled barrel. Sometimes you can get a good dal.

i recomend the brenneke slugs outta of a cylinder or improved choke, works good for me and i can get 4inch groups at 75 yards with no sights

If it is a Mossberg 835, then no. This gun is overbored and Mossberg cautions against shooting slugs through overbored barrels.

This is from the F.A.Q. section of www.mossberg.com ==>

Can I fire slugs through my 835® vent rib, Accu-Mag choke tube barrel?

No, 835 field barrels (those with a ventilated rib) are "overbored", the extra inside diameter may cause the projectile to "wobble" producing unreliable accuracy. A projectile may wedge inside the barrel causing an obstruction. Obstructions of any kind can cause damage to the firearm resulting in personal injury. Dedicated smoothbore or fully rifled slug barrels are available for the Model 835. Other 835 Accu-Mag Choke Tube notes: Buckshot and steel-shot loads are not recommended for use with an Extra Full Turkey tube installed.

The Mouse

I have a Remington 870 that I use to shoot rifled slugs out of. I use an improved cylinder choke which Remington recommends for rifled slugs and I use adjustable fiber optic sights. I can shoot 2 inch groups at 100 yards as long as you clean the barrel after 6 or 7 shots.