save your money and get the rifled/cantilever barrel for your 870, get a quality scope, and try numerous saboted slugs, within 125 yards the shotgun is deadly, and evern further with practice

are you asking if a .30-06 will compare to a slug gun?

there is no comparison if you ask me, rifles will out shoot slugs all day long.

I'm sure there are exceptions as in the worlds greatest slug gun vs. a horrible shooting rifle, but 3" groups at 100yds from a rifle would not be considered "good"

sabot Slugs can, and often do group well at 100yds,but they are also inconsistent(flyers) which makes them in"accurate" IMO. I can think of no reason to choose a slugun where a CF is legal. also, what you save by buying a slug barrel for your SG, you will quickly spend on sabot slugs which run about 2-3$ each, compared to 1$ 3006 bullets.