HELP Please TX200 Mk1 problem

[Wilfy100]

Hi,
I have a problem with my TX200 Mk1. I am unable to get the rifle to cock because the compression cylinder will not travel back. It comes to a complete stop with about 3/8 of an inch still visible in the loading port. If I stand the rifle upright with the barrel uppermost the compression cylinder will fall under its own weight until it comes to a complete stop. If I work the cylinder back and forth it travels from the port closed position until it stops with literally an audible clunk as if something is in the way and stopping it. I can confirm it is nothing to do with the piston, spring,or trigger group as these have been removed, also as it is a Mark 1 it cannot be the anti-beartrap as there isn't one. I have removed the cocking linkage as well so it cannot be that. The rifle was working fine and then suddenly the problem appeared. I had removed the spring and piston about 50 shots previously to apply some moly grease but I did not remove the cylinder at all. I can see absolutely nothing in the main tube that would cause this issue, the cocking slot is smooth and unobstructed. I am unable to remove the cocking shoe because it will not travel far enough to reach the enlarged section.
It definitely feels like there is something solid in the way, it is not just tightness or binding as everything is smooth until it stops dead. I am baffled by this as it is basically one round cylinder inside another, the compression cylinder is sliding in the main tube in an area where apart from the cocking slot it is just a plain tube with nothing there to cause this issue. The stock fixing bracket is forward of the loading port so it can't be that. Just to confirm I had been using the rifle fine, the pellet hit the target and then when I came to re-cock the rifle it would not.
I do not think it is the cocking shoe because with the cylinder held up against the obstruction there is a small amount of free play with the cocking shoe itself, it does not seem to be coming up against anything. Any help or suggestions with this would be much appreciated, I am at the moment up the creek without a paddle. The rifle came from a new and collectable air rifle specialist and has 2 1/2 months warranty still left, but no doubt as I have taken it apart the warranty will de well deceased now. Interestingly the rifle had been serviced by an air rifle tuning/repair specialist (based north of Birmingham) just a few days before I bought it, but it was bone dry of any grease and only producing 9.1 Ft/lbs of muzzle energy. just some lubrication improved this to 10.9 Ft/lbs and I was looking forward to using it.
I must admit to being a bit of a TX200 fanboy, I have a mark 3 and a mark 2SR as well as the Mk1 so I hope it can be sorted, I have studied it carefully and I cannot see anything untoward and it is 100% standard and not modified in any way.
Cheers Wilf

[sherlock1963]

It may be caused by galling inside the cylinder.

The rear end of the compression tube is pushed upwards to ride along the cylinder wall when you cock the rifle. This caused a 'grinding' sound in my first TX (also a MK1) When I stripped it down there was a worn stripe opposite and clearly visible through the cocking slot, at the end was a small burr which caused the sound. The comp tubes on many TXs get a noticeable shine on the tail end where it rubs. Pro Sports have a delrin ring to solve this, a pity TXs don't have one

Possibly yours has gone a little further and stopped the comp tube from passing the burr. A small file or similar may sort out it out and allow you to get the comp tube out to fix the problem.

Hope that helps

[sherlock1963]

or the scope mount 'recoil' pin has been screwed too far into the cylinder.

[Wilfy100]

Sherlock1963 is absolutely spot on. His answer is an exact description of what has happened. I found a worn groove in the main tube with a raised burr at the end of it. I carefully as I could filed this down with a curved Swiss file and eventually the compression cylinder went paste this. However the cylinder then stopped at the limit of its normal travel. I t was really a case of the same thing again but in this case the burr was in the form of a line running round the main tube. Clearly what had happened is the compression cylinder had ploughed up some of the metal of the main tube and left this as a raised lump. The compression cylinder has some signs of wear lines on it but it does not seem as bad as I had feared, possibly it is made of a harder steel than the main tube. I suspect the rifle has received very little maintenance, It seems the the outside of the compression cylinder has even shown some signs of rust spots forming.
I now need to clean out any traces of grease and then carefully polish up any worn areas. I believe this will get the rifle working again, but I think I will need to periodically strip, clean and re-grease the internals. This will not be a big hardship as the rifle is dead easy to disassemble. It does raise the question that can my Mark 2 and 3 Tx200's suffer from the same problem, it seems they can.
There is no stop pin holes on the mark1 so consequently the scope and mounts slide back along the main tube even though the scope is only moderately heavy. I am thinking about drilling a stop hole myself but this would be above the trigger assembly so it would have no effect on the compression cylinder. I will first try a one piece mount to see if this will solve that.
Big thanks to Sherlock1963, his info told me exactly where to look.Just one last question, in my haste I removed the cocking shoe without seeing which way the the square cutout in it went. I think it goes towards the loading port end, could someone confirm this for me please.
Cheers Wilf

[sherlock1963]

glad to be of help.

It's not uncommon to get the 'shiny stripe where the comp tube rubs. Pro Sports have a delrin bearing which prevents the problem. The rust spots on the comp tube (hardened steel) and the burr are almost exactly the same as what happened to me. When I stripped it all down the piston seal was yellow, dried out and cracked. Definitely in need of a proper service.

The cocking shoe will only fit on the arm one way round, the square cut-out is at the front of the action.

While it is apart (and seems to have been neglected a little), you may as well strip the trigger unit. Not too hard and takes about 1 hour, de-grease the inside of the casing, clean all the old dried up stuff from the sears, polish the contact points and re-set nice and crisp. Teflon oil is my preferred lube or a little moly, it will be vastly better than the AA original stuff.

[Wilfy100]

Hi,
Just an update that may be of interest. The rifle is now up and running, I carefully removed the burrs using Swiss files and small carborundum stones. I finished off with very fine grit emery paper to give as smooth a surface as possible.
Also I dressed the rear end of the compression tube so that it had a small rounded chamfer and polished this to a mirror finish. I also did this with the inner edge if the compression tube so that the piston seal did not have to go over a sharp edge. I highly recommend the use of Micromesh cloth to do the polishing, this is very high quality emery cloth that goes up in grades to 12000 grit, 4000 grit and above gives a finish like brand new chrome plating it is that smooth.
I fitted a new piston seal and a TBT drop in tuning kit. To fit the delrin top hat I had to remove the existing steel top hat from the spring. This was much easier said than done, it was absolutely stuck rock solid in the spring. I ended up having to grind slots in the top hat so that I could collapse it to get it out. It turns out that the diameter that goes in the spring has one turn of course thread on it so it has to be unscrewed but even trying to unscrew it when it was partly collapsed did not move it. You could not see this at all because the spring coils are closed up at that end by design. I hate ruining parts like that but I definitely wanted to go with the Delrin top hat. The spring ends were given the smoothing and polishing treatment. It turns out that polishing the spring was a waste of time because I now believe the spring to be well past its best. It is 8mm shorter in length than a Mk2 spring that is relatively new. With the TBT delrin kit in place there is about 4mm of extra preload on the spring and this gives 10.42 Ft/lbs of muzzle energy with the lightest pellets I can lay my hands on, these being RWS hobby at 11.9 Grain. AA Diabolo Field at 16 Grain give a disappointing 8.81 FT/lbs. Since there was not much preload i added an extra power washer 4.25mm thick. This actually made no difference whatsoever, in fact the average muzzle velocity went down from 628 to 625 feet per second using the Hobby pellets. In conclusion I have taken the rifle apart, put it back together now more times than I care to remember, even trying a Mk2 spring in it as I have one available for a future rebuild of my Mk2 SR and I need a break from doing that. Clearly I need to place an order with the very helpful people it Protek for a new Mk1 spring. At the moment the rifle is very good apart from the low power, It is smooth to cock and shoot. I will use it as it is until I muster a bit of enthusiasm to polish the ends of the new spring and fit it. I will be going to the excellent indoor rifle range at Doncaster on Sunday. I want to test the accuracy of the rifle against my Mk3 TX200 in ideal conditions, I suspect that the Mk3 will be better but I will try to find out objectively if that is the case. Overall despite the problems I am glad I have the rifle, the woodwork and bluing is in very good condition. But I think I paid near to top money for it and I have been putting quite a bit more money into it as well as a lot of time. I find some rifles you just take an instant liking to (such as my Mk3 TX200) but this has yet to happen with the Mk1. Perhaps when the new spring is in and I can get just over 11 FT/lbs with the AA Diabolos (the Hobbys will bee about 11.7 FT/lbs so plenty close enough to the 12 FT/lb limit) I will be settled. I don't think this is unreasonable, would any Mk1 owners let me know what muzzle energy they are getting and what pellets they find best please. Yours rather frazzled, Wilf

[Wilfy100]

Hi,
Just an update to the update! I will not be getting a new TX200 Mark 1 spring because to the best of my knowledge you can't buy new Mark 1 springs. I have tried all of the usual suspects and what is available is one spring that covers both the Mark 1 and 2. I believe this is actually a Mark 2 spring as its internal diameter is suitable for a Mark 2 spring guide. While the difference in internal diameter between Mk1 and 2 is not much it will definitely be loose on a Mk 1 spring guide. I have now settled on using the Mk2 spring with a Mk2 TBT Delrin drop in kit. Initially I put this together with the Delrin top hat without the spacer and 2 power washers totalling 7mm together. Power was 10.31 Ft/lbs with the 11.9 grain RWS hobbys. I then added the extra top hat spacer giving an extra 5.5mm of preload. With this extra preload power actually went down slightly, the muzzle velocity reduced by 4 feet per second. I then removed this top hat spacer as it increased the cocking force noticeably and produced no extra power. With this removed power crept to about 10.5 Ft/lbs. I am at a total loss to explain why the extra preload does not raise the muzzle energy. But working with this backwards logic I removed one of the power washers reducing preload by 4.25mm. Low and behold power went up to 10.89 Ft/lbs and after a short target shooting session a recheck over the Chrono gave 10.99 Ft/lbs. So now with the light pellets at least I am getting reasonable muzzle energy, and the Hobby pellets gave excellent accuracy over the admittedly short range I can shoot in my garden. I suspect muzzle energy may pick up slightly as everything beds in. Using minimal preload definitely helps with making cocking easier. Time now to move on to the next issues, I need to put a softwood peg into the top rubber but pad screwhole as the screw has come loose and is providing no grip. Also the u shaped bracket that the front stock screws go into is slightly loose even though the allen screw is fully tightened down. I suspect I will have to remove one pitch from the screw thread to shorten it so it holds the bracket securely. Since the action tube has no stop pin hole the scope slowly wanders backwards, I will drill the action at some point to fit a stop pin. Despite this catalogue of woe I am glad I have the rifle, I will pay a visit to the collectable air rifle shop where it came from and calmly explain all of this to the proprietor. To be fair I have had several rifles from him and I have been well pleased with them apart from this one. All of this goes to show there is an awful lot things I need to learn about air rifle tuning, but that is a challenge that I look forward too. Cheers Wilf (Now not quite so frazzled)

[sherlock1963]

HI, Don't drill the cylinder as this will instantly devalue the rifle. Find a spring set-up that reduces recoil and get a decent one-piece scope mount.
Out of curiosity, what is the serial number?

You should easily get 11+ ft/lb from a MK1 TX. It sounds like it wasn't well treated by a previous owner. I (and many others) prefer the MK1 shorter stroke to the MK3s lazy 96mm stroke. There are many parts available to convert MK3s to replicate the MK1.

As a 'very rough guide' : higher power from light pellets =bounce. A little extra weight in the piston helps. Ideally, same power from 12 grain and 16 grain pellets for a .22
Check/change breech seals and check the compression tube plug is screwed in fully. Removing the piston weight will reduce power.
A sheame you don't live in Essex, I could take a look for you. (PM me if you like)