If you have any questions about these two mods just ask.
The first mod is about increasing power by drilling out the air transfer port between the tank and barrel, the second mod I hope fixes the common issue of broken firing valve pins in the Arrow, which I think results from a lack of firing pin support between the hammer and valve. As for tools and disassembly, not much will be discussed there, it's not difficult, work in a well lit area, etcetera. I'm not a technical writer so do these things on your own or use a pro, but I'm a handy person as should you too before doing these things. Work at your own risk. Read and understand everything before attempting.
For the firing valve mod you should degas the tank, you can loosen the tank gauge, do slow slowly. You can remove the tank first to do this, it's two T25 torx screws under the stock, careful as the nuts will fall out of their slots in the rifle. Then carefully remove the two plastic bands, the rear band will prolly fall off, the front band be careful to pry that off, don't mar it up. Don't use excessive force when disassembling or reassembling.
To remove that band, see the little horizontal slot at the top of the band where it hooks into the stock, gently pry that up with a slim screwdriver of the correct size, don't pry on the band itself or it'll prolly break.
* POWER MOD: No photos are included. A chronograph is required. So with the tank off you'll see the transfer port, remove that carefully by twisting it out, don't mar it with a pliers or anything, don't ruin the o-rings. The only lube you'd use on any of these parts is silicone oil if any at all, anything aerosol or petrol based might erode or explode. I drilled out the port to 9/64 per my liking and went from 690 fps to 820 fps. I used a regular hand drill with the part wrapped in masking tape and drilled it out in stages with the drill bit index, I held the part with a mini vise grips and wrapped the part in masking tape so as not to mar.
Drill it out to your liking, you'll of course need a chono to complete this mod, you'll have to reassemble it to test fire, don't try to fire it without complete reassembly or it flies apart. I think this mod is self explanatory so that's about it, drill it out to your liking.
* FIRING VALVE MOD: The following photos show the firing valve support mod, which uses parts I found at a True Value hardware in the nut display area, those parts are common to those displays; a bushing, five nylon nuts, a nylon screw of the same size (not seen), and JB Weld metal epoxy.
As for the sizes of the parts, I don't remember exactly, only that the bushing fit about perfectly in the space, but it had to be ground down using an angle grinder in a vise to fit in that area. The five nylon nuts fit snuggly around the pin, I think they were 10/24 size if that makes sense. Bring the air tube to the store is what I did. A nylon spacer of the same nut size was a bit too loose on the firing valve pin, so I went with the nuts.
For a lot of this you're on your own, I'm not a technical writer. Grind or cut the bushing to get close to fitting, the gap between the washer hole was finer then the scale in the drawing, like maybe an eighth of an inch. But the only place it's glued is onto the firing valve, nothing is glued to the stock. When the nuts were lined up on the nylon screw, they were lightly super glued.
After they dried very well they were glued into the bushing with JB Weld metal epoxy. I used the nylon screw of the same size to keep glue from the threads. You want those nuts to be as squared as possible so I put it up on a flat surface with a piece of tape underneath, so they'd dry like that and not get stuck. And don't press the firing valve pin unless it's been degassed.
So after the epoxy sets up after a day, the bushing is glued onto the firing valve. Lightly sand the face of the bushing and valve, don't sand or nick that pin or it may damage the tempering. Of course test the bushing before gluing, see that the pin should be snug but have no lateral movement which is what I think leads to it's breakage. I put a very thin coat of teflon plumber's grease on the pin before gluing, put a thin coat of epoxy glue on the bushing and the valve, then press into place. If done well, a bead of glue will form around the glue joint. Use a cotton swab or something to clean up the area if need be.
So now let it cure for at least a full day or longer. Reassemble and hopefully the pin won't ever break. I'm not a technical writer so proceed with your due diligence.
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