In all honesty my friend, I think that you are using those cheap calls too much.

If the bird is responding, and more to the point COMING IN to those calls, but then hanging up at 70 (or more likely 80 as thats the magic number) then it is likely because you are over calling. The gobbler wants YOU to come the rest of the way. Remember, hens go to the gobbler's 9 out of 10 times in the wild, so over-playing your hand, or being a little too aggressive on the calls can hurt you.

Try soft purrs and scratching the leaves! Nothing works like a little leaf sratching.