Das Mafia,
If you can shoot 6 inches now then 4 inches will come with practice..Now rev up the motor and shoot the minute the sights are lined up, fast as you can but not rushed to the point that you give up accruacy...Most folks hold the gun to long and squeeze to long and muscle fatigue sets in and the tremors start....I think a controled flinch is what I have...

If you cannot improve that 6 inch group, then by all means you will get by and your now better than most by a good deal....Keep your ability and your range coordinated together, if the game is beyond a 100 then find a rest..knowing your limitations is the best shot you have in the hunting fields...