Robert, 1000 yards sure seems to be pushing the envelope with that type of weapon. It seems to me that hitting a target at that distance has got to be more art than science.
A guy I used to work with once told me that his Army unit in Vietnam occasionally used a sight-mounted .50-caliber machine gun as a long-range sniper weapon. He said it was used when his outfit was set up on a hill to "reach out and touch someone" across a valley. The distances at which he claimed they got kills were positively supernatural.