Let's plug this into the handloads.com ballistic calculator, shall we?
According to their tool, a 180gr., .400", "SWC/HP" style bullet, launched at 1000fps, will still have 439 fps of ass behind it at 1000 yards. Of course, you'll have to "hold over" 286 FEET to get it there, assuming a 25y zero. It would likely still be able to cause death at that range.
It doesn't drop below 700 fps until 365 yards. The .38/200 and .38 Special killed an aweful lot of people with similar ballistics.
I've repeatedly nailed a man-sized gong at 400 yards with my .22LR...using 20-25 FEET of hold over.
Point it, range is more dependent on the launching platform, the amount of time allocated to the shot, and the skill of the operator than the projectile or its velocity.