I’m in metro Detroit. I can ship/PayPal. I’m away from home for the week, but I can send you more info about what I have available once I’m back downstate. It shouldn’t cost much to ship across state. I usually do FedEx, and get excellent rates through my work.
As far as your velocity problem, it still sounds like a compression issue. It’s easiest to check hop up and bucking seal first, some aftermarket buckings vary in thickness. Madbull buckings are thicker and sometimes don’t work with VFC hop up units just as an example. Any variation in the OD of the new barrel can create issues. If you’re using a ribbed bucking like a Maple Leaf, they usually get an awesome seal out of the box.
You could also have cylinder or nozzle leaks too. You really can’t tell unless you open the gearbox to check. Generally if you drop an M120 in and your getting less than 380 there’s a compression problem.
Should be noted that I’ve seen many good guns develop intermittent compression leaks in the cold. Seals shrink and expand depending on temperature. I’ve seen a Krytac pulled out of a cold car chrono at 240 FPS and an hour later after use gain 90 FPS once warmed up.
All that said springs do fatigue over time. So it could be the spring too. Especially stock springs that aren’t tempered or are made from inferior alloys.