TX200 cocking shoe

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Ozwald

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Nov 26, 2021
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B.C, Canada
I had a problem with my O rings being eaten up on the barrel seal. I noticed that there was a gap at the back of the cocking shoe that let the spring push the piston cylinder forward when fired and was letting the nipple for the o rings hit the barrel slightly.
I went ahead and made the cocking shoe bigger with silver solder and it now fits tight in the slot on the chamber, I now have 5 thousands of an inch clearance from the barrel when locked up and does not hit the barrel anymore.
The only thing that holds the nipple from hitting the barrel is the cocking linkage as I can see. Would it be a wise idea to machine a delrin ring for the piston chamber to rest on when the barrel is locked up to save the linkage from slamming stress?.I don,t know if this is a good idea or not, looking to the experts for advice. Thanks Steve!
 
You might get a little bounce and lose breech seal pressure if you do that. The double orings should absorb the forward motion of the comp tube on the shot.

There is variation from rifle to rifle and headspace from breech end of barrel to breech seals are one of those areas.

Did you lengthen your cocking shoe on the trigger end or barrel end? As you close the cocking linkage are you feeling the orings starting to compress right before it latches?

Steve
 
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Yes I did the front end of the cocking shoe barrel end to see if it would tighten it up a little, and yes I can just start to feel the o ring just before it touches the ball bearing for lock up. But then I milled off the end of the nipple as it was touching the barrel,only a couple of thou. When it is locked up there is 5 thou clearance from the barrel.
I am not sure what the clearance should be from nipple to barrel. maybe you could help me with that. So the idea of milling a delrin fitted washer over the barre into the front of the action is a bad idea then. Thanks Steve!
 
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Ozwald said:
Yes I did the front end of the cocking shoe barrel end to see if it would tighten it up a little, and yes I can just start to feel the o ring just before it touches the ball bearing for lock up. But then I milled off the end of the nipple as it was touching the barrel,only a couple of thou. When it is locked up there is 5 thou clearance from the barrel.
I am not sure what the clearance should be from nipple to barrel. maybe you could help me with that. So the idea of milling a delrin fitted washer over the barre into the front of the action is a bad idea then. Thanks Steve!
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I’m not sure on the exact clearance recommendation. I recently pressed the port insert out of a TX and machined the face down for this same reason. As long as it’s not tappong the barrel on the shot, you’re good to go.

Steve
 
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Nitrocrushr said:
I’m not sure on the exact clearance recommendation. I recently pressed the port insert out of a TX and machined the face down for this same reason. As long as it’s not tappong the barrel on the shot, you’re good to go.

Steve
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Thank you Steve I had the same problem, When the gun was cocked and closed there was a gap of about 2-3 thou. but when it was fired the transport nipple hit the end of the barrel that's why I milled the end of the transport nipple.
That's when I started looking at the cocking shoe the gap at the rear end of the shoe made me think of the slap of the piston chamber hitting the barrel. So I guess there is some bounce when fired.
I am still thinking of the delrin spacer that touches the piston chamber when closed to stop that bounce. I may be off in left field here, I think I will try it to see what happens cant hurt anything. Thanks for your help Steve. Steve! lol sounds like an echo.
 
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Two weeks ago I had Motörhead work on my 10 year old TX MKIII.
The black nut on the end of the compression tube was unscrewing and making the cocking stroke longer preventing the safety from engaging. He took care of that.
Re-assembling the rifle he noticed a little slop between the 10 year old cocking shoe and compression tube.
He fashioned a SS sled that the cocking shoe rides in, completely eliminating the sloppiness.
 
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Frank in Fairfield said:
Two weeks ago I had Motörhead work on my 10 year old TX MKIII.
The black nut on the end of the compression tube was unscrewing and making the cocking stroke longer preventing the safety from engaging. He took care of that.
Re-assembling the rifle he noticed a little slop between the 10 year old cocking shoe and compression tube.
He fashioned a SS sled that the cocking shoe rides in, completely eliminating the sloppiness.
Click to expand...
A sled? Wish I had thought of that; much simpler than casting/milling a new shoe!

-Marty
 
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Thanks for the highly informative and helpful posts. My breech seal also got chewed up after around 4k rounds, but this is probably within spec. Yesterday, accuracy started dramatically deteriorating and the only thing I could find that may have caused it was the breech seal (see photo below). Interestingly, the muzzle velocity didn't change. If the culprit really was an eroded breech seal, it suggests that the breech seal pressure on the barrel may be important to accuracy (perhaps changing barrel vibration or piston/compression tube bounce or something else?).

Headspace in the TX200 is pretty complicated so please let me know if this is right. The position of the front of the transfer port (breech) is set by the front of the compression tube pushing up against the barrel nut. The cocking lever should pull the front of the compression tube tight against the barrel nut, so it helps to put a spacer at the front of the shoe to make sure the cocking lever pulls the compression tube forward, tight against the barrel nut. If the headspace is right, the breech seal will be squeezed the right amount between the breech and the end of the barrel. If the headspace needs to be increased (piston seal is squeezed too much or the breech is actually touching the barrel) a spacer can be added to the front of the compression tube or the breech can be bored a bit deeper, moving the seal/breech face back. If the headspace needs to be decreased (breech too far from barrel so the piston seal not squeezed enough to seal properly), one would have to remove some material from the front of the compression tube. The cocking shoe should not be stopping the compression tube from going forward when the piston hits the front of the compression tube. Please let me know if this make sense?

Thanks,
John

breech_oring.JPG
 
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There are 2 breech seals. You need to replace both at times as both can compress. I do not do both every time. I probably should.

Your description sounds correct, but the spacing should change very little, so if it was correct at the start it should be now. Unless there was some other issue.

The velocity does not have to change a lot to mess things up. Usually, for me, it is the variation in one or 2 shots that starts me thinking about a breech seal replacement. It becomes an issue of intermittent sealing first.

To me your seal needs a replacement. Perhaps both.
 
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