OK you have the full power valve installed, you will need a .22 barrel and a .22 bolt, with the barrel and receiver removed from the rifle, slide the barrel itno the receiver and install the set screw that holds it in place, drill out the port in the bottom of the barrel to .170 inches, try to get the port right in the middle of the hole in the bottom of the receiver, most of the time thay line up perfectly, remove the set screw and pull the barrel out of the receiver and deburr the port on the inside of the barrel, I use a 5/32 inch sharpening stone for a chain saw to remove the big stuff and then wrap 220 emery paper around a drill bit to begin smothing the area, work your way up to 600 grit to get it real smooth, the same method can be used to smooth the loading tray for the pellet, be careful not to bugger up the area where the o-ring for the probe seats, it's the raised area just inside. For the bolt you can center drill for a probe, use a 1/16 inch bit, the bit will self center when you do this, drill in about 1/8 to 3/16 inch, no need to get to deep here, cut the probe off just behind the port, check by assembling the barrel, receiver and bolt and make sure the cut off probe doesn't block the port you drilled in the bottom of the barrel, if it's clear of the port then you can insert the drill bit and measure from the shoulder of the bolt out 1 3/8 inch, mark the drill bit at that length and cut it off, a drop of super glue will hold it in place. I you don't want to try the extended probe, use some wire size drill bits and drill out the end of the factory probe taking about 5 or 6 thou. at a shot, it will take a few changes of bits until you get to around .170 inches, then drill out the port in the bottom of the probe, don't drill the port out first, you may twist the end of the probe off if you do, If you should need seals or o-rings let me know and I'll send a set or two to you, good luck, if you should have problems let me know, I'll do what I can to help. Mike