Hello, I have the M3 with 600MM barrel and 480 CC canister on order and I am trying to decide what extended rail to use. I am looking at the Saber Tactical and noticed they have a standard version and a compact that is for the 300 CC can. I will often shoot the gun on the farm from the truck window or on top of a fence, and for a few weeks a year leaning against a tree shooting squirrels . So I you have a Impact with either rail please let me know what you think .