I did some chronographing of a GP100 4.2" and 3" with different types of ammo. The results are interesting. Just that one inch of barrel length makes a difference when shooting magnum loads. Lighter, faster bullets will have more velocity gain in the longer barrel. https://lh3.googleusercontent.com/-iWL1ZYLy6ME/Tx9SCcnWEkI/AAAAAAAAAZc/hUOzEVkklqI/s885/gp100s.jpg Wanna kill these ads? We can help!