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Old 1st October 2016, 10:19 PM
Bellerophon Bellerophon is offline
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Default AA TX 200 MK 1 v Mach dramas

Evening all.

Ok so as a tiny bit of background information I've decided to reintroduce life into a TX200 mk1 in .177 that has been locked away in my gun cupboard for a few years now. I've just fitted a v Mach kit and the rifle is only going over the chrono with 8.44's between 722-730 Fps. With previous internals I was only achieving 740 Fps with the exact same pellets. I've tried adding additional washers but that has no real affect.

So it's led me to think possibly the rifle is leaking air on firing. I've done a small amount of googling and it seems that the if under lever maintaining tension on the piston it can cause this. I've removed the underlever retainer from under the barrel and cocked and load the rifle and the under lever won't stay in its desired position, it drops approx 40mm below the barrel. So is it safe to assume that there is no tension being applied to the piston when firing thus causing air to leak from the breech as there isn't a seal.

If this is the case does anybody have a fix for it?

I'd appreciate any input.

Thanks again,

Kieran
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  #2  
Old 2nd October 2016, 05:01 AM
hmangphilly hmangphilly is offline
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did you size the new piston seal ?

how are your breech o rings looking ?

new spring in the kit ,or using the original mk1 tx ?

i would have expected to see a bit more than 740 from std spec ......

Last edited by hmangphilly; 2nd October 2016 at 05:05 AM.
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Old 2nd October 2016, 10:19 AM
Bellerophon Bellerophon is offline
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Quote:
Originally Posted by hmangphilly View Post
did you size the new piston seal ?

how are your breech o rings looking ?

new spring in the kit ,or using the original mk1 tx ?

i would have expected to see a bit more than 740 from std spec ......

The piston seal seems a good fit for the compression tube. I've used the new spring supplied in the kit and I've replaced the breech seals also.
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Old 2nd October 2016, 11:19 AM
hmangphilly hmangphilly is offline
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Kieran,

Rob spoke to steve pope recently .
steve put quite some emphasis on getting the seal fit just right .

it's very difficult to gauge , but if you are using the complete kit as supplied i'm guessing its just that the seal might be a bit tight .

we devised a kind of method of comparison of seal fitting by fitting the piston in the tube , standing it vertical and measuring how many tins of pellets it took to make the piston travel down the comptube .

i even made a gadget to enable us to do it no handed

i'll see if i can dig up a pic


just scroll thru this you'll get the gist..........might help

http://www.shooting-the-breeze.com/f...ghlight=effect

Last edited by hmangphilly; 2nd October 2016 at 11:28 AM.
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Old 2nd October 2016, 03:19 PM
Bellerophon Bellerophon is offline
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Thanks that makes for a good read with some interesting points.

I've been shooting mine today and it doesn't seem to be particularly hold sensitive, no POI movement between stances and it can shot off of the floor (HFT prone position). I have only been shooting at 27y but thus far it shoots ok. However in my opinion I could do with an additional 20-25fps.

I'm going to put some more pellets through it to about the 750 pellet mark and then re-chrono. I have emailed Steve Pope with my findings. In theory it would add up that the piston seal is too tight within the compression chamber as the washers make no difference to the muzzle velocity.

Just out of curiosity what lubricant are you using around the piston seal, I've only dabbed the tiniest amount of Molly grease around the outside edge of the seal.
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Old 2nd October 2016, 05:05 PM
Kcjohandby Kcjohandby is offline
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Ayup mate it depends on the pellet to.tx barrels seem to vary in size alot im tuning one now n he sent me aa 8.44 in 4.52 which seem very tight in barrel so i put my jsb 8.44 in 4.53 n i git a difference of 30 fps without doin anything so check tht aswel.as for the vmach kit cant say much bout them but took one out of one im tuning cause the seal went they dnt seem to be very gud seals but just my opinion
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Old 2nd October 2016, 06:43 PM
Bellerophon Bellerophon is offline
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Originally Posted by Kcjohandby View Post
Ayup mate it depends on the pellet to.tx barrels seem to vary in size alot im tuning one now n he sent me aa 8.44 in 4.52 which seem very tight in barrel so i put my jsb 8.44 in 4.53 n i git a difference of 30 fps without doin anything so check tht aswel.as for the vmach kit cant say much bout them but took one out of one im tuning cause the seal went they dnt seem to be very gud seals but just my opinion
I've tried a variety of pellets and they haven't changed velocity by more than 10fps. Ive not really had a lot of experience with V Mach kits but I've heard nothing but good things about them. I'll be intrigued on what the outcome of this is from Steve, just out of curiosity what seal are you using?
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Old 2nd October 2016, 06:45 PM
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Nick G Nick G is offline
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Make sure your comp tube end plug is sealing
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Old 2nd October 2016, 06:46 PM
Bellerophon Bellerophon is offline
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Make sure your comp tube end plug is sealing
Sorry to sound a bit green but how would I go about checking that?
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Old 2nd October 2016, 07:41 PM
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Nick G Nick G is offline
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Quote:
Originally Posted by kieran turner View Post
Sorry to sound a bit green but how would I go about checking that?
Put your finger over the trans port and pull the piston rearwards to its full travel release and it should travel back to its forward position, or do it the other way round , ie finger on trans port push piston forward and immerse in water , look for air escaping.
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