Here's what it says on the Chuck Hawks
page about sierra
Sierra
Sierra Pro-Hunter bullets are the best selling bullets on the market. They are conventional soft point bullets with tapered jackets and flat bases. They are known for accuracy and fast expansion, which leads to quick kills on CXP2 class game. Pro-Hunters come in flat point, semi-pointed, hollow point, round nose and spitzer form, depending on caliber and intended use.
Sierra GameKing bullets are conventional soft point or hollow point spitzers with tapered jackets, but tend to feature high ballistic coefficients. All are boat tail designs. Their terminal performance and application is similar to other soft point bullets, producing quick kills on CXP-2 class game such as deer, antelope, and black bear. GameKing bullets intended for larger game simply have heavier jackets and harder cores (lead alloyed with antimony). The .375 caliber, 300 grain spitzer boat-tail, for example, has an extra-heavy double-taper jacket and a core of 3% antimony lead alloy. Sierra bullets have a reputation for extreme accuracy, which I have found is deserved. Often when I receive letters from readers with accuracy problems, my first suggestion is to try a Sierra
bullet.
http://www.chuckhawks.com/big_game_bullets.htm