Pretty new to shooting and just recently purchased my first real gun...HK USP .40 Variant 2 (DA/SA with safety/decock on right side). When you aim a pistol, isn't the correct method to line the dot on the front sight up even with the two dots on the back sight to make a straight line? When I do this with the fixed sights that came on the new gun, the gun actually tilts down, as if putting the front sight dot between the rear sight dots is not correct....any advice would be appreciated....