A 15" target is not going to range with much of anything at 1500 yards, the beam size is just too large. A PLRF or Vector will hit a 24x18 target at 1400-1500 pretty well, but a 18x40 at 1800 is a no go. Can the Terrapin range past 2K? Certainly, but not on a 15" circle. 1 Mil at 1500 yards is 54 inches. To get a reliable reading, most units are going to need to reflect at least 50% of the beam off the object. A PLRF 10, for example, is .3 x 1.5 mil divergence. so the beam is 16" x 81" at 1500, or about 1300 square inches. If you figure 50% of the beam return, you'd want a target no less than 650 square inches and a 15" circle is only 172 or so. You'd need a target a little over 30" in diameter to get a reliable range. The Terrapin beam is a bit bigger. Note that the specified performance for the Terrapin is 1800m on the NATO target, which is 2.3m x 2.3m. It will range reasonable targets past 2.5K for sure, but it can't be tiny.