question about reloading

[millerlite]

i started reloading about a month ago. i am reloading for my .308 rifle. i was looking in the book that i have and the loads were test from a 22in barrel. since my rifle has a 20in barrel i was wondering how much, if any, velocity do i lose. thank you for your help

[UVvis]

You should see about a 50-100fps drop in velocity. There are a ton of variables at work that will influence this, so you'd pretty much have to shoot your load over a chronograph to be sure.