Hope I am not breaking a rule here but the following came from the Smith and Wesson forum in their ammo section. Again not my testing.
2" S&W M337:
High 800 fps
Low 799 fps
Yes, a total for five shots of 1 fps variance.
3" Custom Colt Agent:
High 859 fps
Low 855 fps
Extreme spread of 4 fps.
4" S&W M67:
High 889 fps
Low 885 fps
http://smith-wessonforum.com/ammo/51...ial-p-hst.html
Extreme spread of 4 fps.