GTA
Airguns by Make and Model => Air Arms Airguns => Topic started by: inmhs on October 11, 2020, 02:30:50 PM
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I got a walnut TX200 HC .22 from AoA a couple of days ago. It's a really pretty rifle; the stock just needs a little more finish.
The first thing I noticed when I cocked it was the effort. It's lots higher than my full-power HW77k .22. I'd like to reduce the cocking effort and smooth the shot cycle. I'm fine with reducing the power some.
I have some experience tuning airguns, I have a small machine shop and have made lots of spring guides and various other parts. If I tune this myself I'll probably order a new spring from ARH, and make tight delrin guides, and maybe new bearings for the piston if they aren't snug. Maybe an O-ring seal.
I've read lots lately (last few days, just joined this forum) about Tony Leach's 22mm conversions. Does anyone have experience with these in a low-power tune for a .22 HC?
Any other ideas for a really nice shooting tune?
Thanks, Mark
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Shorter barrel and shorter cocking arm over the TX MK-3 full size = MORE cocking effort :P
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That makes sense, but why is it so much worse than the 77k?
What tune would you recommend for moderate to low cocking effort, moderate velocity, minimum recoil?
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I had some spare time, so I opened the TX up to see what it was like inside. Lots of dark gray grease. I took out the piston and compression chamber, machining looked good, piston seal was too tight, but not terrible. It looked almost new inside, barely shot, consistent with the outside. The spring was very loose on the steel guide, and on the massive steel tophat. It was around 29 coils, 0.130" wire. I looked around in my parts drawer, and found a nearly identical spring, but 0.113" wire, trace smaller ID, with a delrin tophat tightly fitted. Probably from 5 years ago or so when I was tuning my ProSport, not sure.
Anyway, I cleaned up the insides, tophat was a great fit, and the spring was a tight fit on the factory guide.
With the factory spring, very hard cocking effort, lots of vibration and recoil, about 680fps with 14.3 Crosman pellets. With the new spring, very light cocking, almost dead, pellet stays on the scope cap, 550fps with the same pellets.
I'm very happy with this as a first attempt, taking about an hour. I think I'll shoot it for a while and see how I like it.
I'm very likely to finish the stock better, the wood is really nice, maybe try an O-ring seal (there was one in the drawer), maybe do something so the link from the cocking rod doesn't slop around. Might disable the beartrap. My full-length TX is a MK1, so I"m used to no beartrap.
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While Motorhead was tuning my TX200, I laid on Jim Maccari's Royal London Oil to the walnut stock. I opted for his professional method. Came out very well. Satin finish.
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I've always used Formby's or Minwax tung oil finish, but have read so many good things about Maccari's that I would like to try it. It's out of stock. Do you know of another source for it or something similar?
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Not all is paradise. I decided to address the slop in the cocking link, so I removed it, this time I noticed that the holes in the cocking arm were oval. This is not at all consistent with the rest of the rifle, which looks almost new. On closer inspection, it looks like someone intentionally enlarge the holes on the side to the back, maybe to loosen lockup? They opened them up around 0.02", not very consistently. I'm pretty sure the front edge part of the holes is original, it still has a bit of chamfer there. It looks like there's plenty of material left, and that if I open the holes up to 0.25" (from around 0.196" originally) it will clean everything up. I'm not quite sure how to locate the holes, probably I can get very close using the radius of the remaining factory part of the hole. I might clean up the cocking arm first, then use that to locate the link hole.
Should I set it for compression-chamber to barrel contact with no barrel seal?
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Also, the front of the cocking shoe has been altered, don't know how much has been removed. It would be nice to set it up correctly with a shortened shoe, then just put in a stock one if it gets loose.
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Forgot to add, all the parts that are messed up can be bought shipped for less than $70, so considering the stock I would buy it again.
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Try for a pic?
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And that's with the so-so finish.
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Test?
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It seems that I can't do pics anymore. Maybe not enough posts?
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Egg pic
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No pic. Retry.
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Smaller file?
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Finally worked. Top left edge of the hole shows factory bevel, bottom right shows whitish ridge of metal, looks like it was enlarged intentionally. If I stay centered on the original hole, opened up to 0.25", should remove all the defects.
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Hey, Mark. Looking good. Lovely stock, that one. The brits love their sub 12 FPE 22's. There's just something "right" about the lazy thump of the shot cycle. You might try a power washer to bring the power up a tad. I"d opt for a larger wire diameter, probably around .120" give or take. Can't remember what all Maccari has for these rifles, but they shoot dandy at the 12 FPE level. Over that they seem to be reaching too hard to get there.
Yes, your problem with posting pics was probably low shot count. Welcome to the forum!
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I can't wait to see the stock with a little work. It seems almost unfinished, lots different than the older ones I've had. I probably will bump the power up a little, but with tendonitis in my elbow now I'm very happy with the low cocking effort.
Thanks for the welcome.
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I got ambitious a few hours ago and decided to fix the cocking arm. I put the arm in the mill, and aligned it off a pin gauge through the holes that the arm pivots on. I opened up the damaged holes with a 1/4" end mill, they were so bad I ended up going to 19/64. I made some steel bushings and pressed them in, all seems well now. No more slop in the link, should last a long time.
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This picture didn't send first try. The bushing and the new big hole.
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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...
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If I want to bump up the velocity a little which end of the spring should I put a spacer under? Does it matter?
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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.
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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?
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To light of a piston will cause a power loss, That's why the steel hat is in there, inertia, ;)
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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.
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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! :o
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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.
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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.
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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.
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The transfer port has a flat on one side. Is this factory?
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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?
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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.
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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.
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One more.