TX200 HC .22 tune

[inmhs]

This picture didn't send first try. The bushing and the new big hole.

[AmBraCol]

Nice work.  Yep, there's a lot to be said for an easier cocking rifle.  Flat out top velocity shouldn't be the only measure of a rifle, in my considered opinion.  I'm in the midst of setting up a Crosman Optimus to sub 12 FPE. It's a much nicer shooting rifle than when it came from the factory.  Now I'm eyeing the Cometa Fusion with a jaundiced eye as well...

[inmhs]

If I want to bump up the velocity a little which end of the spring should I put a spacer under? Does it matter?

[AmBraCol]

If I want to bump up the velocity a little which end of the spring should I put a spacer under? Does it matter?

It depends. Some folks will use a heavier "top hat" front spring guide. But since you're not seeking top power, you'd probably be better off putting a spacer at the rear end of the spring, over the rear spring guide.  Make sure that it will not interfere with the piston latching in place. Also, if you use a synthetic (delrin, etc) it's a good idea to use a steel bearing surface for longevity, just factor in the thickness into the preload adjustment you're doing.

[inmhs]

I'm sort of confused about this. It seems like lighter pistons reduce recoil, but AA has a big steel tophat in the stock TXs. I remember Maccari used to (maybe still has) a steel tophat in some kits. Why might the extra weight be better?

[Mark 611]

To light of a piston will cause a power loss, That's why the steel hat is in there, inertia, 

[inmhs]

I've been trying to read up on this, and remember what I did 20 years ago when I was really into tuning my airguns. I think I need to balance piston weight (including tophat) and transfer port size. It looks like it would be pretty easy to make interchangeable transfer ports, so I might do that, and try to make a light piston. From reading about some of Tony Leach's stuff, it looks like if I make the transfer port out of delrin, I might not need a seal.

[Mark 611]

Dude I just noticed ur in INDY? I'm in Columbus IN, if ur thinking about interchangeable TP ports if its not done correctly ur asking for trouble!

[inmhs]

Indy. Was heavy into FT in the late 90's. MCF&G.  Do I know you? Shot a TX200 shot when AS ran FT, I ran it with him one year?

If the surface presented directly to the chamber pressure is greater than the surface at the seal-barrel interface, the transfer port should be pushed forward during firing, apart from the pressure drop, which I think would be trivial (think, can't back it up). I think. Just need the hole in the piston to be bigger than the sealing area of the barrel.

[inmhs]

Just read this again, the pressure drop would always drive the port to front, unless the piston was bouncing, or the port was extremely restrictive.

[inmhs]

If the surface presented directly to the chamber pressure is greater than the surface at the seal-barrel interface, the transfer port should be pushed forward during firing, apart from the pressure drop, which I think would be trivial (think, can't back it up). I think. Just need the hole in the piston to be bigger than the sealing area of the barrel.

That made no sense. Should have been "Just need the hole in the compression tube nut to be bigger than the sealing area of the barrel." Still not so good. I'll try to make a drawing.

[inmhs]

The transfer port has a flat on one side. Is this factory?

[inmhs]

I'm editing this to say, I just searched some more and I think "my idea" is very similar to some others out there. Is this close to Tony Leach's old design?

The one on the left is factory, blue is the inside of the part that screws into the compression tube, orange is transfer port, black circles are barrel seal.

My idea is on the right, remove factory transfer port, slide a delrin piece in place, o-ring around the outside, flat delrin face to seal against the barrel.

Any opinions?

[inmhs]

The Maccari Royal London Oil showed up yesterday.

Today, I took the stock off, the recoil pad off, and cleaned the stock twice with rubbing alcohol. I was surprised how much the grain raised.

I put a coat of the RLO on and let it dry, to hold the raised grain up. The stock seemed dry in a few minutes. About an hour later I did a second coat, cut in with 400 grit w-d sandpaper. I plan to do another coat with the 400 grit in a few hours. So far, happy with the progress.

The RLO seems very similar to the Formby's Tung Oil finish I've used in the past. Might dry a little quicker.

[inmhs]

Done with the finish. I ended up doing three coats with 400 grit, then two more with 600 grit. I let it dry for four days, then waxed it with Renwax. I'm happy with the finish, the grain is filled and the surface feels completely smooth. The RLO was very easy to use.


I think I'll shoot it this way for a while before I do any further tuning.

[inmhs]

One more.