Mine shoots low at 100 yards if I use a six o'clock hold on the target like I do with all my other rifles.
I shot a match with my Underwood last weekend, just for fun, and thought, what the hell, I'll just cover the (10-inch) target with the front sight blade and shoot with a 12 o'clock hold.
I've never done that before, but it worked great. I got 2nd place in the match. So I will probably just leave my front sight alone rather than trying to file it to the perfect height.
