TX200SR dissassembly

Re: TX200SR dissassembly

Postby FPoole » Thu Dec 21, 2017 1:31 am

I'd count on a new piston seal for sure. The piston seal will go bad just sitting in a cabinet. Had several that were maybe 5 years old in a sealed baggie. I took one out and it busted when I tried to install it. I took the others and all crumbled when I squeezed them. These were the translucent slightly yellowish ones from the 2000 era. The new clear ones seem to be tougher, but I always use an Apex seal from Maccari.
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Re: TX200SR dissassembly

Postby ChrisW » Sat Jan 06, 2018 6:36 pm

Now I have the spares from Julian, the SR is now stripped down to virtually individual parts. I can't believe how much grease there was to clean off of literally everything, some of which almost looked baked on in places :o Thankfully everything is in great condition, but new breach seals and piston seals and bearings will be going in anyway.

My only concern at this point is that the power was a bit hot prior to stripping, but there is only one additional washer I can remove from the spring guide and there was virtually no preload on the spring when I started. If I start needing to collapse/cut coils I fear the spring will be too short and will rattle around in the available space. Has anyone come across this problem with their TX before?

Also, could anyone tell me what the screw in the front of the trigger block is for? Its the only part I came across that had me stumped.

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Re: TX200SR dissassembly

Postby FPoole » Sun Jan 07, 2018 8:36 pm

Maybe the new piston seal has a tighter fit and will slow the gun a bit. I don't think negative preload would be good. That screw is also something I really don't know about. I think the cocking link pushes against it when the action slides forward at the end of the cocking stroke. I left well enough alone.
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Re: TX200SR dissassembly

Postby ChrisW » Mon Jan 08, 2018 7:27 pm

See those were my thoughts initially but I don't think the cocking link does push against it.

After dissassembly + reassembly my current theory is that the rear edge of the piston pushes against the little stub extending from the sled into the cocking slot in order to push the whole action forward on the rails and lock it forward once the piston is latched and until the rifle is fired. If this is the case it would essentially pull the action forward onto the end of the piston at the end of the cocking stroke, rather than pushing the latch rod all the way back into the action. This could also explain why it takes that little more effort at the end of the cocking stroke to latch the piston in the trigger sear. Or something like that, I'm still not convinced by that theory and I'm sure in reality its much simpler than that :?

I'm happy to be enlightened otherwise but if I'm right that still means...what's that screw for :lol:
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Re: TX200SR dissassembly

Postby FPoole » Wed Jan 10, 2018 11:30 pm

The MarkI uses a hex head bolt instead of the allen headed bolt. Not any help, but it is a point of interest and difference.
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Re: TX200SR dissassembly

Postby TenMetrePeter » Thu Jan 11, 2018 9:08 am

If it was a pusher or even a deadstop it would have shiny marks on the end. Does that cross hole have a thread and grub screw?
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Re: TX200SR dissassembly

Postby FPoole » Thu Jan 11, 2018 9:23 pm

I'd have to take my gun out of the stock, but I'm pretty sure there is a shiny spot. The hole has no threads, so no grub screw.
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Re: TX200SR dissassembly

Postby ChrisW » Fri Jan 12, 2018 6:51 am

Mines coming apart again tomorrow for some fine tuning after getting it down the range this week. I'll take some more pictures of bits for reference.
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Re: TX200SR dissassembly

Postby FPoole » Fri Jan 12, 2018 1:00 pm

Was just told by another SR owner, Cloverleaf on the Airgunforum, that the end of the cocking link contacts the screw head near the end of the stroke and pushes the whole action forward. I guess you are lifting the action and compressing the last bit of spring to lock up and that's why it gets harder to cock at the end. I had to visualize the cocking action to get a mental picture before it made sense to me. The first stage of cocking is normal, until the tip of the link hits the bolt/screw head. This stops rearward movement of the cocking link, but the action is still rearward and not cocked. The forked end of the cocking arm then levers the whole lot forward, pivoting on the cocking link pin.
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Re: TX200SR dissassembly

Postby ChrisW » Mon Jan 15, 2018 8:17 pm

I can understand the theory behind that mechanism during the cocking action, it's odd that there are no wear marks on either the bolt head or cocking arm though. The previous owner really must have barely used this rifle from new! So if that way of cocking is correct, in my mind, winding that screw out a bit would make the cocking action a little easier potentially. I might have to have another tinker at the range this week.

I still think the action must be held forward by the piston contacting the stub protruding from the sled into the rear of the cocking slot. I can't see how it could happen any other way without the action sliding rearwards if the action was tilted back.
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