TX200 won't group

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Lewis

Lewis

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May 2, 2015
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Eureka, California, United States
I have a TX200 in .177 that is terribly inaccurate. I'm getting 5 inch groups at 15 yards! I thought I had a bad scope on it so I switched to a proven scope from another gun, no change. Barrel is clean and looks good. The shot cycle feels much rougher than the shot cycle on my other springers. I have tried many pellets and several holds including from bags. All internals are stock and look to be in good shape. I'm thinking about getting a 12 foot pound kit. My best guess is that the seals aren't sealing.

Any ideas?

What kit to go with and from where?
 
Wow, that is terribly inaccurate. How new is it? Does it just need some breaking in? I found with mine that the pellet head size made a vast difference in how it groups. I bought a pellet gauge and sized up the different tins that I have and found the size that it likes best. Between different brands it will shoot very similar groups as long as the head size is the same. I had a gen 2 TX200 with a 12 ft lb Venom (now V-mach) tuning kit in it and that gun was awesome. Unfortunately, as is often the case, I sold it in search of the next one that might be just a little “better.” I have replaced it with a mark 3 TX200, but that mark 2 is the only gun, of many, that I regret having let go. Good luck in your quest for a solution. 
 
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That HARSH shot cycle leads me to think the main seal may not be doing its job and /or the breech seals may be leaking a lot. While apart, did you test the main seal by pressing it in while holding a finger over the breech to see if it seems to hold air well. Another thing to look at is when the gun is cocked, is there any forward/backward play between the compression tube and the barrel. This can be tested by using a finger or two on the compression tube and trying to slide it forward and backwards. If so then the breech seals need replacing. or the cocking shoe is worn and not holding the compression tube close enough to the barrel. If you need a set of 2 breech seals then shoot me a PM and I will send you some.for no charge. 
 
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Thanks for the replies. I will check the seals as suggested. I do have a chronograph, Ill check that too. The gun is an earlier mkIII. It has the stock before the fish scales. When I purchased it I was told it had very minimal use. It looks new and may well still need breaking in.

I am considering a 12 ft lb kit and all new seals. I bought it with that in mind. 

Any recommendations? 
 
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I have one of those older Mk II rifles also. It has a shorter 83-84mm stroke than the newer Mk III's that have 91mm stroke and is highly cherished. Due to age and neglect, mine had a totally shot main seal which is very common with standard AA seals. You can identify an OEM Mk II spring by its having 2 collapsed coils on one end. It also has a LONG steel tophat that can be replaced with one of delrin also.

FYI, Air Arms only changed to 91mm stroke when they introduced the Mk III to allow more than 12 Ft # to compete with Weihrauch in the US market. 
 
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The Mk II has many evenly placed anti beartrap grooves on the compression tube where the Mk III only has 3 and the front 2 are close together and the third spaced a little further back..... Here's my MK II apart and a stock photo of a Mk III

1531094232_420329005b42a4d867dba1.03174460_tx200-91.jpg




Mk III

1531094260_21247690475b42a4f4c157d8.54259223_Mk III tube.jpg





 
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I have onl;y seen one thing cause groups like that in a TX ( naturally your results will vary) .

The nut that holds the barrel loosened.

AA had an entire batch come through a number of years ago , 1st of the fishscale I believe but no matter, with poor qc loc-tite on that nut, it may be a pain but well worth checking if nothing else stands out.



John


 
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That HARSH shot cycle leads me to think the main seal may not be doing its job and /or the breech seals may be leaking a lot. While apart, did you test the main seal by pressing it in while holding a finger over the breech to see if it seems to hold air well. Another thing to look at is when the gun is cocked, is there any forward/backward play between the compression tube and the barrel. This can be tested by using a finger or two on the compression tube and trying to slide it forward and backwards. If so then the breech seals need replacing. or the cocking shoe is worn and not holding the compression tube close enough to the barrel. If you need a set of 2 breech seals then shoot me a PM and I will send you some.for no charge.
Click to expand...

what he said
 
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Okay, so I broke out the "lie detector" today.

Suspecting seals I conducted the tests with a fairly heavy pellet to provide some dampening.

https://imgur.com/lWslwNf

High

https://imgur.com/5yMhU58

Low

https://imgur.com/10DXeGI

Average

https://imgur.com/6k8g6Hh

Extreme Spread

https://imgur.com/ioLD2Sw

Standard Deviation

https://imgur.com/OyP6mh1

https://imgur.com/1Vpi0rP

With the 10.34's averaging 384 fps for 3.39 ft-lb.

Well THERE'S your problem!

Tomorrow I'll get it apart and see what's causing all the fuss.

I have a 12 ft-lb Vortek kit, barrel seals and an additional new factory style piston seal.


 
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Got it disassembled today.

1533436944_15141260745b666410160a87.32670056_IMG_1074.jpg


This ain't right.

1533436786_5926173185b666372bbe649.72253842_IMG_1077.jpg


Debris in the chamber.

1533436830_12784229855b66639e5f0d77.93451882_IMG_1076.jpg


Center tube broken off from the base washer.

1533436876_9272950735b6663cc1a4510.49240235_IMG_1075.jpg


Out with the old, in with the new.

1533436920_7075653215b6663f8a51057.73844425_IMG_1073.jpg


Polished the compression tube while I had it out and radiused the safety button.

1533437069_5489703635b66648d933b52.11912001_IMG_1080.jpg


New numbers.

High

1533437118_16520586195b6664be52abe7.03122017_IMG_1081.jpg


Low

1533437142_1432534525b6664d6204fa5.78698724_IMG_1082.jpg


Average

1533437161_3557786395b6664e9bee8b7.11604446_IMG_1083.jpg


Extreme Spread

1533437183_16418682365b6664ff747671.70907611_IMG_1084.jpg


Standard Deviation

1533437207_7511930255b666517d37099.14183844_IMG_1085.jpg


That's more like it!

10.71 ft-lb with none of the washers added.

Also happy to report accuracy has returned!!
 
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