A friend of mine has a Taurus handgun in 44 magnum. With rear sight as far as possible to the right, the handgun still shoots 4-5 inches to the left at 25 yards. Any thoughts as to what the problem may be? Sights installed off center of bore? He had limited $$$ and purchased this handgun used-I guess that could have been why it was in the used bin. Thanks...BCB