Ok, here ya go. had to work it in between rain showers. I couldn't get a measurement on the protrusion and my camera sucks at close ups. Ok i'll have to post this and them edit it to get the pics. hang on a couple minutes.
A 22 will be fine, mine is a 20. never checked the speed of the bullet but I know it will knock deer off their feet at 700 yards. A 22 sounds perfect to me.