Just a long-time owner of an SL-68II, then looked at a picture of a "I". Looks like the same bolt. One thing I've found on my II is that the mainspring loses it's tension after a number of years, making it impossible to get the velocity up above 220 eventually. Stretching it helps, but at a certain point it just has to be replaced. Honestly, I've never really liked the "block the air flow" method Tippmann used for adjusting the velocity.