Just read an article on range finders, you can range as far as you want but it will cost $$$$$. Personally I am more into small cals. but for 1000 yard PLUS ranges I still say you will do better with something like a 300 SAUM shooting a heavy, high BC bullet at high velocity. Compare the drop charts for some of the cals. mentioned in this thread and you will see what I mean. Richard Franklin ( I think ) had a good article on accurate shooter about 1000 yd groundhogs. I don't enjoy shooting big cal. guns so I shoot my 20 vt, 204, and 223 ack imp at the longest range that they are capable of.