P68-AT was working, but…

[James_Blond]

So I had a complete and working without leaking AT, However it is super dirty and only shooting around 200FPS. So it needs cleaning for the hammer to move faster and maybe shimming. However, problem, the front banjo screw is stuck and the Allen head is stripped out, was already pretty rounded out. Looks like I’m going to have to slot for screw driver.

In case it goes sideways, anybody have or know where I can get a new banjo screw?

Might have to do the hombrew wedgits to make this playable. Probably won’t keep it long term, but do want to play with it before parting with it.

[Toestr]

Maybe try Bacci or I'm sure someone on here has a stash. It's reasonably easy to drill a bolt to be a banjo if you have a drill press.

[Carp]

Bacci definitely has some NOS...banjo screws. Mcmaster may also have what you seek.

[James_Blond]

Yeah, a drill press is on my list of tools I should get at some point. For some reason I didn’t think of Bacci.

[James_Blond]

At $18 each NOS is pricey. Those clippard screws he has don’t look to hard to modify.

[Carp]

I totally agree with the "sticker shock". Heck, if you've got the tools and the determination. Run to the local hardware store and grab a small bag of 1/2" 10x32 button head screws. All boils down to spending some time and a little less money. Or spend less time and a little more money. 😉

[James_Blond]

Ok, so this front banjo is STUCK. Slotting the head didn’t work. Had to resort dremeling the head off the screw completely. Then it broke off at the hole. I”m left with a bit of a stub coming out. Couple questions. Will this screw prevent me from backing out part of the cartridge valve? Was hoping to get the cup seal out before resorting to high heat. So far my bolt extraction pliers aren’t moving it. I’m afraid to apply to much force and shear it off.

Any suggestions to minimize damage?

[Cal440]

No pro here, but maybe you could direct some heat with a strong 110 volt soldering iron and a vise grips with good teeth. Sometimes it takes just a little persice heat to help. Or would a easy out in the hole work?

[James_Blond]

Tried an easy out on the head of the screw. Complete garbage product, at least the ones I have. I think we have a soldering iron around somewhere. Torches I have but like I said trying to avoid melting whatever seals are still stuck inside.

[JeeperCreeper]

Have you tried heat? You're gonna torch the valve seals, but they are just orings and are cheap and probably need replacement to start with. You might also need a new valve pin, but crossman 2250 valve pins fit. You need to heat the brass, not the fitting. You want to expand the brass so you hopefully break it free. Then grab it with vice grips and give it a twist. Worst case scenario, you have to drill it out and tap it for a 1/8 NPT fitting. Hope this helps.

[JeeperCreeper]

https://www.ebay.com/itm/302034076312?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=2Q0YM1uwQ3S&sssrc=4429486&ssuid=nudjnr6vros&var=&widget_ver=artemis&media=COPY

[James_Blond]

Some direct heat with a propane torch, grabbed it firmly with my knipex twin grips and it got it out without any more fuss. So a victory there. I got the valve nut out with some force to break free, but nothing too bad. Now I’m just looking at the valve stem. I assume this is old style valve which is leaded in. Looks like i just need to dig the lead out to get the rest of the valve out, source orings for a rebuild and make some new banjo screws. Also thinking of adding wedgits, and maybe a quick strip slot. Suppose I don’t really need a quick strip with the spring loaded lug on the speed demon, but kinda fiddly in the middle of a game.

Gun is P-series p008290

[BrickHaus]

Your valve tool should have a threaded end. It should be able to thread onto the valve half to pull it out.

I haven't been into ATs, but I do believe part of the valve is soldered in.

If you can see a 12g face seal looking from the front, send a wood dowel into it. If it's a solid soldered plug, I think pulling the valve with the tool is your only bet.

[James_Blond]

Thanks, I had entirely forgotten about the threaded part of the tool. Looks like, I’ll have to pull it, just working on getting the lead out of the way first.

[James_Blond]

So, got the lead out of the way. Sticky says I should be able to replace it with a 014, if I’m reading it correctly. Valve does have a soldered plug at the back. Gun was shooting around 200FPS and bottom tube needs to be cleaned up. Mainspring has a coil cut off, Looks like I have a spare full length and some similar springs from the hardware store to try on the valve and mainspring. I have a female stab coming for velocity adjustment, still looking for a UMB for it. Would like to get it shooting hot and then reg it down.

The banjo screw orings are urethane. Any reason I couldn’t replace them with buna 70? The end screws have buna orings. I plan on running the gun on co2.


Oh, and the cup seal got hot enough it squished out and not it seats so deep it kinda sticks to the valve body. Suppose I’lll order a couple off of eBay and just cut the 12g pin off.

[Jordan]

You can use Cocker cupseals on Sheridans, if you happen to have one kicking around.

The lead seal isn't actually a seal, it's there for assembly line purposes to retain the valve before the jam nut is installed. No need to reinstall or substitute an oring in place of it - it does nothing.

Are you planning on using HPA or Co2? Either way, increasing the transfer port size from valve to bolt is a great idea. HPA may require higher output pressures than normal because of the small valve chamber volume - my PMI build uses a dummy 12gram as a volumizer and I have a reg on it set to 350psi, roughly, to get 275fps. I've also increased the port sizes on the valve, body port, and bolt.

[Jordan]

I do every Sheridan I modify the same - 7/32. Same as PPS.

The other part of the mod is tapping the hole you drilled (in the bottom of the lower tube) and adding a setscrew to orient the valve ports vertically when you reinstall the valve - much like a Cocker.

I also port out the top valve transfer port and fill the circumference of the valve with epoxy to make sure every bit of air goes through.

In all honesty I think the extra volume in front of the valve makes the biggest difference, but the valve work and increased transfer port size got me to the mid-30s (shots) per 12gram on my KP2.

[James_Blond]

So the thought occurs to me, that being a back bottle Sheridan with the external air line, which has 1/16” air holes through the banjo screws, is all the porting of the valve and body going to do much? It would have better flow valve onward, but air is very restricted prior to the valve. I will have some added volume from braided line to the asa, but still choked at the external air line.

[Jordan]

My understanding is that those small passages might slow down the recharge of the valve's dump chamber (the pocket of air in front of the valve) but it really shouldn't affect velocity under normal rates of fire.

Increasing the area of the transfer ports, in both the valve and between the upper and lower tubes, will help with extracting the maximum velocity potential of the dump chamber charge. If I'm understanding the theory behind the modifications.

IF the transfer tube and associated hardware flowed well, in theory it could "bandaid" the dump chamber volume, much like how using a gas-thru grip on an ICD 'Cat adds volume in front of the valve to help with HPA usage.

[James_Blond]

Hmm, didn’t think I did, but I have a black cocker cup seal from some gun some time ago. I went ahead and ordered 3 Sheridan valve stems. I have a pmi-1 which probably still has its original stem, and a ton of p-12 and pursuit pistols, so I’m sure i could use them up or move them when I sell some of those guns. Plus I’d rather keep the cocker seal free in case I need it for one of my cockers.

So with the lead seal gone what seals the valve in? There weren’t any orings in it anywhere when it came apart. I would assume I would need something.

CO2 build.