I have a smoothed bore Benelli M2 (26") shotgun.  Would that be ok to hunt deer with using Foster slugs?  Or should I get a inexpensive rifled barrel shotgun?  

no need for a rifled barrel with slugs. It all depends on what you gun likes. My Ithaca M37 w/ 26 IMP has all 5 holes touching at a measured 100 yds using 7/8 ounce Win slugs. When i went to 1 oz ones it opened up to 1-1/2  at 100 yds.

Does it have rifle sights on the barrel?... Most people use smooth bore, so i don't see it being a problem at all..

I have an 21 inch M2 field and shoot slugs out of it all the time.

As mentioned, make sure you have some form of adjustable sights on it, be it a red dot, iron sights, or scope. A bead sight is not legal to hunt with slugs in NJ.

Thanks for the replies  Yes, I'll make sure to have sights on it.  I'll try out some foster slugs to see how they group with different brands.  Is the IC choke generally the best for slugs? 

Thanks for the replies  Yes, I'll make sure to have sights on it.  I'll try out some foster slugs to see how they group with different brands.  Is the IC choke generally the best for slugs? 

Yeah, improve cyclinder seems to be the choice... definitely not anything with a tighter pattern.

Thanks everyone.