38 special or 357?

[CPJ 2.0]

Well, back to the drawing board. To answer the above question, and I didn't even try the math on fpe yet because I was just assuming that it wasn't at the 200fpe mark yet, but my shots were between 789 and 798. So now that I actually used the online calculator I see that I'm at 209fpe. BUT, there's always a catch and I ran into this when I built my 50 air rifle, I'm having an issue balancing performance and reliability. It's alot to get into but it's either get a high velocity and tear up seals or make it robust and get lower velocity so now I'm back to staring at the wall while the wheels turn, but I'll figure it out eventually. I'm just tired of pulling this thing apart and putting it back together.

I don’t know exactly how how it comes apart, but know how a regular 2240 comes apart….I’d wager it’s similar and it sucks a big wang.

[Justsomedude]

Well, back to the drawing board. To answer the above question, and I didn't even try the math on fpe yet because I was just assuming that it wasn't at the 200fpe mark yet, but my shots were between 789 and 798. So now that I actually used the online calculator I see that I'm at 209fpe. BUT, there's always a catch and I ran into this when I built my 50 air rifle, I'm having an issue balancing performance and reliability. It's alot to get into but it's either get a high velocity and tear up seals or make it robust and get lower velocity so now I'm back to staring at the wall while the wheels turn, but I'll figure it out eventually. I'm just tired of pulling this thing apart and putting it back together.

I don’t know exactly how how it comes apart, but know how a regular 2240 comes apart….I’d wager it’s similar and it sucks a big wang.

I've gotten so good at that part that I can get it to where the valve is out in about 2 minutes. It's disassembling my valve that is the PITA and the repetition. I did mull some ideas over in my head last night in my insomnia that I think might give me the balance between reliability and power. I'm betting there's a reason that nobody else has come up with this idea. It almost seems impossible.

[Castle]

Go work on something else for a bit. The solution will come to you.

^^^This is great advice^^^

Sometimes your too close to the problem you don't see the solution... take a break, work on something else.

[Justsomedude]

Go work on something else for a bit. The solution will come to you.

^^^This is great advice^^^

Sometimes your too close to the problem you don't see the solution... take a break, work on something else.

This is true. I learned that as a mechanic. Sometimes a job would kick you in the ass for what seemed like forever to the point that you wanted to throw a wrench only to go to lunch, come back refreshed and whatever it was would go easy and smooth.

[Japhy]

My guess is though not familiar with the design is high pressure seals? The instantaneous temperature from atmosphere to 2000+ psi is going to be very high. Either different material or a method to dissipate or transfer the heat away from vulnerable materials or maybe both. Just my two bits.

[Justsomedude]

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Done some more to it today. Got the rear piece done that ties the back of the breech to the pressure tube and made a cocking knob.

I am also honing in on the reliability issues and everytime I solidify one thing, the problems become less. Im awaiting some specific orings and I think it'll be complete AND have plenty of power still. It's dumping all of the tube so I'm going to try to add a block in the middle of the pressure tube with a small orifice to limit the volume of the shots. I'd be happy with 2.

[Justsomedude]

My guess is though not familiar with the design is high pressure seals? The instantaneous temperature from atmosphere to 2000+ psi is going to be very high. Either different material or a method to dissipate or transfer the heat away from vulnerable materials or maybe both. Just my two bits.

I really wish that I could discuss the workings of the valve but it's as close to having a money making idea if I've ever had one lol. I can understand why nobody has thought of it, because of its complexity although simplicity. I know what the problem is with it, it's just trying to find a balance to make it seal but not cut them when it does its thing. I'm now into buying some extremely expensive orings, especially for ones that are so small.

[CPJ 2.0]

Is a lapped metal to metal sealing surface an option?

[Justsomedude]

I actually tried that already. Dealing with these pressures absolutely requires seals. And seals that work in a dynamic way too.

[Gila]

Have you tried using copper seals/o-rings/gaskets?

[Justsomedude]

I didnt realize there is such a thing. Tell me more.

[CPJ 2.0]

Copper seals are used on head gasket etc on race cars, make good sealing. But, that’s a static situation. I’d wager they would get beat to poop with valves slamming shut.

Have you looked at o rings for hydraulics?
They would handle the pressure and then some. But, they aren’t made for the violent slamming.

Or maybe order something from a store bought air gun to see if what they use would work?

Delrin or UHMW or Teflon ?

Or….I may know a guy.

[CPJ 2.0]

The dude who makes these days he uses polyurethane seals.

[Wambli Ska]

Haven’t commented because I’ve been stupid busy and just doing drive bys here. HIGHLY interested in your progress, just not much to add to the discussion except amazed at you capabilities.

[Justsomedude]

What I'm dealing with is high pressure, fast moving air blowing my oring out of its groove and that's a solid ptfe oring. I've tried plastic and it won't seal.

[Justsomedude]

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Update
I got tired of messing with my new valve design so made a more compact version of the valve that I invented for my 50 caliber, still top secret .

The pistol is now reliable and can be shot without issue. Also cut dovetails and installed sights. I bought some 83 grain .358 pellets that won't register on my chronograph that maxes out at 1100fps! It's an airgun chrono. This thing is ridiculous. This valve isn't as powerful as the experimental one but it's close and it's reliable. I thought I was testing 148 grain bullets but they are 158 grainers that I was getting almost 800fps at.

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[bullsi1911]

That is awesome.

Can we see some damage from it hitting a target? To you have any gel to shoot it into?

Could you use .38spl hollow base wadcutters in it?

[Justsomedude]

I have launched wad cutters through it but not hollow based. I'll take a pic of the damage that it did to a pellet trap when I get in the shop tomorrow. It hits very hard for an airgun.

[Justsomedude]

Oh, and no gel although that would be a fun experiment. I hear it's fairly expensive?

[Wambli Ska]

Still following closely!

[bullsi1911]

Oh, and no gel although that would be a fun experiment. I hear it's fairly expensive?

It’s not too bad. I think my block was like $75.

[Justsomedude]

As promised. The swinger is 1/8 thick steel. The housing is doubled over 1/16 steel. The back of the trap is tapered so the bullet struck it, dented the hell out of it then went down and dented the bottom of it too. Second shot on Mr Ram who didn't fair too well. These were the 82 grain pellets.

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[PFD45]

Dang!
That is NOT the Crossman that I grew up with.

[Justsomedude]

Just for kicks I sent one at a 3/4" thick piece of aluminum. It put a small impression in it but the wad cutter looks impressive.

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[PFD45]

Was that some hard aluminum?

To "expand " a wadcutter like that must have put a real smack on it.