More Airsporter help please

[Airsporter1st]

This is a simple mechanism, in which anyone with a bit of methodical measurement/comparison could diagnose the cause of the reported problem, with ease.

With all due respect, several people (e.g. Guy ggggr) have made solid suggestions and/or observations, which you seem to just ignore, preferring instead to post more pictures and questions.

Perhaps you should take the gun to an airgunsmith, or see if a knowledgeable/experienced member lives near enough and would be willing to help you out.

[philcbr]

Which suggestion have I ignored? I have assembled the gun minus the spring and reported my findings, mostly using pictures.
As I have said pushing the piston in to trigger block by hand works fine.
The threaded section attached to the trigger block has been shortened by a previous owner for what purpose I do not know, I can only speculate on that.
Baz has supplied measurements from his piston that are different to mine so I have concerns in that area.
As I do not know the history of the gun I’m trying to gather as much information as I can to find a possible solution to the problem.
In one of your replies you suggested the trigger was assembled incorrectly, however when I posted more pictures from a different angle you said it looked ok. In another reply you suggested the piston rod might be short, I agree with you that might be a possibility.
I also agree with you this is a simple mechanism, but if the parts have been altered they might not function properly when assembled.
As I do not have another gun to compare parts with I seek the experience and knowledge from members of this forum, even you.
I note you are a well-established member of this forum so I guess you have more knowledge than me on the subject of spring powered airguns. I’m sure whatever knowledge you have on the subject came from asking questions and having a go at repairing things yourself.
If you are fed up with me asking questions and posting pictures just ignore my post, simple.

Phil

[philcbr]

Following further enquires it does seem the piston rod is approximately 6mm short, I have no idea how this has occurred.
I am considering trying to disassemble the piston to establish if it has been modified?
Does anyone have information regarding the manufacture of the rolled piston assembly? I know it is brazed together but in what order. There looks to be three parts, the piston rod. Rolled tube and the piston end that the leather seal fits on.
Has anyone taken one apart? Any information regarding this procedure would be appreciated.
If this is not a practical proposition then I will have to consider trying to purchase a replacement piston.
Many thanks.
Phil

[Airsporter1st]

If I remember correctly, the cocking rod - i.e. the bit you have determined is short - is removeable. Problem is, I don't recall how it comes out, but I think it should unscrew. If you look on Chambers site they are advertising the piston as 'complete' with rod', which reinforces this. (£66.00, by the way)

If you look down inside the piston from the rear, you may see a slotted nut, in which case you need to make a wrench from a suitable tube, with two raised lugs to engage the slots in the nut and unscrew it.

In theory you could make or have a new rod made. The difficult part will be case hardening in way of the trigger sear.

[T 20]

If I remember correctly, the cocking rod - i.e. the bit you have determined is short - is removeable. Problem is, I don't recall how it comes out, but I think it should unscrew. If you look on Chambers site they are advertising the piston as 'complete' with rod', which reinforces this. (£66.00, by the way)

If you look down inside the piston from the rear, you may see a slotted nut, in which case you need to make a wrench from a suitable tube, with two raised lugs to engage the slots in the nut and unscrew it.

In theory you could make or have a new rod made. The difficult part will be case hardening in way of the trigger sear.

The MK2 doesn't unscrew, Paul.

The whole lot is brazed together, the rod is brazed into the end cap, then the body is brazed on.





All the best Mick

[philcbr]

Thanks for the replies.
I suppose I might just as well get the blow lamp out and get on with trying to take the thing apart, I have nothing to lose as it is of no use in its current state.
Shame the new seal is not removable without damage.

Phil

[Airsporterman]

Okay - so you have established that the cocking rod attached to the piston is too short - that's where the problem lies then!
If you say you can get it to work by pushing the piston back by hand, I presume you mean the rod engages correctly with the trigger mechanism - then that must mean that the spring is becoming 'coil bound' before this can happen when assembled - ie, the spring length is too long for the short length of the piston rod.
if so, you have 2 choices.
1. Shorten the spring - which is what I would do - this will allow you to use the existing short piston rod? Taking some coils off to shorten the spring will sacrifice some power, but these rifles were only supposed to produce 10.5 ft/lbs at their optimum anyway and will shoot probably with 8 ft/lbs + okay - remember, you want consistency over power!
or 2. Replace the piston/rod assembly with a second hand one from another rifle - they can be bought on the bay and other places.
I wouldn't be messing with the piston/rod assembly personally - but if you have the time and skills - go for it.

Does this make sense with any of the othe Airsporter 'guru's that know more about this than I do?

If I'm wrong - then just ignore me!

ASM