what distance does a 3-1/2" 12g #4 w/extra full choke have?

Depends on your gun....mine's good to 45 yards.

I tried several different combinations on my Benelli SBE (3.5") and finally settled on a Comp-N-Choke aftermarket choke tube with Winchester HV 2 oz loads in size 5. This was a rather extensive trial and error off a bench rest to determine what works best in my particular gun. Bottom line is my gun patterns best with this load and I would be extremely confident that it could cleaning take a turkey at 45 yards as long as I did my part. That said, I've killed quite a few birds with this set up and as I recall the longest was 38 yards. Knock on wood, nothing I've shot has escaped thus far.

PS. Too late this year, but I'm thinking I've got to try Hevi-shot next year as the patterns I've seen with it out of my buddies gun with his set up have been awesome.