[Cossack]

Both are essentially 200 yrd guns for ground squrrels ( I shoot both). If you're looking for more accuracy and reach consider the 204. Going K Hornet won't increase your range much. It will keep the cases from stretching as much and (may) affect accuracy a bit. But the slight powder increase won't amount to more than 100 fps. increase, which you can do by using light bullets.
I agree with Billy, the Model 40 looks like a real winner albeit it's a single shot.