I don't know what you have tried, but I think a lot of guys go straight for "extra full" chokes and expensive loads, trying to hit on a combination that provides long range patterns. But because there are so many shot (lead vs. other stuf) and load (duplex, triplex, etc) types out there, it is not always easy to find the best combination for your gun.

I've never tried anything but the standard full accuchoke in my Mossberg 500, and with "cheap" Win Super X 3" #5 loads it will kill turkeys out to 35 yards no problem. That's good enough for me. Besides, spending $5 per shell makes me wince more than a turkey load testing range session.