Lets play with the JSB's first, you need to know your speed and your #2 pressure, then take that little metric Allen, get the knob between 7 & 1 and hit the little screw, do one half turn clockwise, moving it out. DO NOT WORRY if the gun won't cock, that just means it was already out a bunch, just turn int back in. If it cocks, then fire a couple of pellets to establish speed, keep moving it until it falls off, then start screwing it back in 1/4 turn increments in until you hit max, then 1/8 turns or smaller to find the sweet spot of max speed, then back it off a bit, you should be good to go. With those pellets you'll be around 900-920, toss in the slugs and they'll be about 980-1040. If your gun doesn't have a carbon tube over the soda straw liner I'd invest in one, you don't have to glue it on, I've got one both ways glued and slip on, zero difference for me.
If you want to get adventurous, you can take of the dial, taking care not to lose that little ball bearing, then pull the HSA and measure the OAL height with some calipers. FX sets them at 19.3mm to start. prior to reassembly, squirt a little lube on your hammer and spring, and use a dab of grease to hold that ball bearing in. It doesn't matter where you line up the dial. I work over a LARGE white towel so with any luck it'll catch that bearing, otherwise....I got out to my collection and open the bag of 50 and grab a new one. Lube the inside of the adjuster too, it's soft Aluminum, just any decent grease works fine.
