How about video taping or using a camera to get a shot at them at 75 yards and shooting them with a shotgun at 35yards. That way you get the bird and can still hunt him next year. I have been doing this for 20+ years and have accumulated a large library of stubborn birds fanning and drumming just out of range. But the joy of reliving those experiences through the videos is alot more satisfiing to me than the memory of shooting one. If the season is winding down and you feel you desperatly want some breast meat and a fan on the wall then I think its fine to use a rifle.
If everyone used a rifle for turkeys I think it would have a very adverse effect on the population. Just my opinion.
You also might try a few more different tricks to see if you can draw those birds in closer. Flap a turkey wing, scratch the ground, use a decoy spread with a small jake and give the decoys some movement.Have a hunting partner sneak off away from you and the gobbler, calling a little as he goes. I have used this method successfully at least once every season to get those stubborn birds in. Good luck[:-]