First you have to know the ballistic data for your load:

http://www.powerbeltbullets.com/docs/PBB28inchballistics.pdf

Then you can plug it into a ballistic calculator like this one:

http://www.handloads.com/calc/

Then you have to try your particular gun in the field to work out the final details. I generally sight my gun in to strike dead on at 100 yards. That is my own particular maximum range since I hunt with open sights. With that, I can just hold dead on without even thinking about it.

As far as how far your load would be lethal, try this link:

http://www.loadammo.com/Topics/July02.htm

I Know what you are using would be plenty out to 150 yards. If you want to shoot beyond that, you might as well hunt with a rifle.