125 yards with a rifle is easy. For a "sniper", it should be a 100% hit potential.
At that distance, the accuracy of the pistol isn't the issue, but the accuracy of the shooter. Assuming the sniper was in any way concealed from view (prone, behind a tree, etc.), then I'd say one or two hits, in a hail of thirty rounds fired, would be reasonable. 25-for-30 wouldn't be realistic at any distance, beyond execution-style.
I've shot a .45 at a 36'x18' steel plate at 115 yards, and was able to hit it, but not every time, and certainly not the first time, as it took a half-dozen rounds to figure out where to hold to hit it.