Sizing seals in springers

[FPoole]

I seem to have learned a lot about TX cylinders from this thread, as well as about sizing seals. I certainly was fooled by the cross hatching into assuming it had ben properly honed, but I noticed the tube has clearly been rubbing oppsite the shoe recess. I have no internal mike to check with, but the gun was running with only a few fps variation with the old piston and seal, so any variation in diameter shouldn't be a problem. It is now back together with a tight (but not ridiculously tight, as it was out of the box) seal, but only giving me 9.5 with 42mm preload, I suspect due to the tight seal. I'll put some pellets through it in the garden tomorrow, then see if that improves things.
I don't think I am brave enough to try Tony's idea of boiling the whole assembly - has anyone tried it?

Don't worry too much about the comp. tube since they are probably as good or better than anything else out there. There can always be a bad one, but I had one professionally honed and it was very near perfect, from the factory except for the ABT notches. Still only had a 9 fps spread with 20 pellets straight from the tin. Not sure if they are still this good as this was a 20 year old Mark3. Won a couple of state titles and shot many sub .5" groups at 50 m with this gun. The divot on the inside that is just opposite the cocking shoe recess on most tubes isn't a problem because it isn't in the swept area of the seal.

[TonyL]

You little tease, you. TonyL will be getting ever so excited (but they do look good)

You know me so well, JB.

I'll be very interested to get to know more about these rings, though.

BOING!

[Vernal]

Michael I have a selection of used tx seals Shall U send you one, I can select one and try it in a brand new tube I have here .

That would be really kind thank you Nick, and would let me find out if the seal really is the problem before I go on to mutilate anything else.

[Vernal]

Nearly half a tinful through oday, and still 9.9 _ time for a seal change

[Vernal]

if you are building this for benchrest, and you are shooting one holers, I'd leave it alone

The story of my life I suppose - never know when to stop!

[hmangphilly]

The story of my life I suppose - never know when to stop!

stop when you start going backwards

[NickG]

That would be really kind thank you Nick, and would let me find out if the seal really is the problem before I go on to mutilate anything else.

Ok will look one out tomorrow

[Shed tuner]

have you checked your breech seals ? Not sure how old the gun is, but that can compress and go hard over time...

[Vernal]

have you checked your breech seals ? Not sure how old the gun is, but that can compress and go hard over time...

Replaced them shortly after I bought the gun a few months ago.

[BTDT]

Replaced them shortly after I bought the gun a few months ago.

On reading the thread, I'm not sure of you have an AA or HW piston seal, but with a Mk.2 piston rod and Mk.3 mainspring, 41mm of preload should get you comfortably over 11 ft. lb. with the AA seal. a little more with the HW, unless air is leaking somewhere.

As Jon suggests, I'd look again at breech seals and, if you are sure they're OK, remove the piston and cylinder, then test for air leakage past the cylinder end plug thread by sealing the outlet with your thumb and manually pushing the piston up the cylinder.

Well worth persisting with; TX200s with 85mm strokes and Mk.3 springs took the top three places at the UKAHFT national recoil championship last year.

[Shed tuner]

Well worth persisting with; TX200s with 85mm strokes and Mk.3 springs took the top three places at the UKAHFT national recoil championship last year.

back in the day (not back in your day Jim, but in my more recent past )I took many titles with my home tuned TX200 HC - guess what ? 86mm stroke No doubt it's a sweet spot for these rifles.

[BTDT]

back in the day (not back in your day Jim, but in my more recent past )I took many titles with my home tuned TX200 HC - guess what ? 86mm stroke No doubt it's a sweet spot for these rifles.

Back in my day?

I can think of a few more titles you richly deserve

85mm or thereabouts of stroke gives enough air mass and enough available piston stroke to avoid overly high peak pressure and temperature, so it's not stressed in the low to mid 11 ft. lb. region.

[TonyL]

And, talking about "back in the day", showing how right the HW77 prescription was for sub-12, back in the early 80s. With a tad less stroke, too.

[Shed tuner]

And, talking about "back in the day", showing how right the HW77 prescription was for sub-12, back in the early 80s. With a tad less stroke, too.

yes, but it had a shorter (and smaller dia) TP, so less lost volume..

[Vernal]

On reading the thread, I'm not sure of you have an AA or HW piston seal, but with a Mk.2 piston rod and Mk.3 mainspring, 41mm of preload should get you comfortably over 11 ft. lb. with the AA seal. a little more with the HW, unless air is leaking somewhere.

As Jon suggests, I'd look again at breech seals and, if you are sure they're OK, remove the piston and cylinder, then test for air leakage past the cylinder end plug thread by sealing the outlet with your thumb and manually pushing the piston up the cylinder.

Well worth persisting with; TX200s with 85mm strokes and Mk.3 springs took the top three places at the UKAHFT national recoil championship last year.

I am using an AA seal,new from Chambers, but it is still much tighter than it seems should be. I had the same problem problem when I carried out your "simple tune " on my LGV,and you were kind enough, correctly, to point out then that the trouble was likely to be a tight seal. Resizing the seal, very time consuming, completely solved the problem, which is what caused me to start this thread in search of the best way to resize a seal. Nick G is kindly going to send me a run in seal which should confirm that the seal is the problem, or tell me to look elsewhere.