well, the stock washer may just have to go back in. I do not have a "how-fast-a-ma-jig", but WOW the M4-117 is running HOT

All I have to go by is impact signatures in my targets from before and after mod, and the sound the round makes when it hits the target. Noticeable change.

I may have to put the washer back in as this "configuration" of rifle would be restricted if shooting over 500fps due to its appearance.

Super pleased with the rifle tho, accuracy is real nice and with no kick at all it is real easy to shoot like you know what you know how to ;)