I'm Sat Waiting On Postman Pat

[evert]

As far as I can make out, Tone, they're the same stroke as the HW50, so about 65mm, which would tie in with John Walther's Airgun book which tells of a HW55 model that used a HW50 cylinder and barrel latch ?

Hopefully I can stretch the stroke to around 72mm but I may be able to go a little more, it's very difficult to give an exact figure until I've measured everything up a few times.
I can't work measurements from the HW50 I have in bits as I have a 99 barrel on that which moves the cocking lever about 3mm forwards of it's normal position.

All the best Mick

How long has your stroke ended up Mick? I seem to remember that you bad some breech void issues?

I have a mild case of the flu, so been tested for covid, and not allowed to leave the house for some days until the test comes back...

Which means I have some time to work on the old rusty HW50s!
I had an extra piston, and has machined it down as much as I dare, plus added a steel seal converter so the piston can take Diana/AA seals.
Had to lengthen the cocking clearance in the piston a few mm's and the stroke is now somewhere between 73-74mm.
Put in a brass tophat from another HW50 project, and a ARH/JM E3200 spring.

The gun behaves quite well during firing, but I have no idea how fast it shoots, as the chrono in in a box somewhere...

[T 20]

How long has your stroke ended up Mick? I seem to remember that you bad some breech void issues?

I have a mild case of the flu, so been tested for covid, and not allowed to leave the house for some days until the test comes back...

Which means I have some time to work on the old rusty HW50s!
I had an extra piston, and has machined it down as much as I dare, plus added a steel seal converter so the piston can take Diana/AA seals.
Had to lengthen the cocking clearance in the piston a few mm's and the stroke is now somewhere between 73-74mm.
Put in a brass tophat from another HW50 project, and a ARH/JM E3200 spring.

The gun behaves quite well during firing, but I have no idea how fast it shoots, as the chrono in in a box somewhere...

Hi Evert.

By coincidence I looked at jumping back on this on Monday and ran the action over the chrono, it's only running at 520fps so I'll be going back in to her pretty soon so I'll measure the stroke for you.

I'm thinking now that I could have lightened the piston too much or I could need more weight and a different Spring, as luck would have it I found a couple of new Titan springs in the pile which will fit the piston at 18.35 mm OD.




All the best Mick

[T 20]

How long has your stroke ended up Mick?

Had to lengthen the cocking clearance in the piston a few mm's and the stroke is now somewhere between 73-74mm.
.

Ah, Evert.

Embarrassingly, and weirdly, after a quick measure I only seem to have a 66.5mm stroke. --- I thought I was over 71mm.

I'll double check in the morning and strip the action down again but it looks like I'll have to machine up a custom piston.
Alternatively, perhaps I could use a 99 piston and just replace the body with a 25mm one, depending on the 99 piston's length.



All the best Mick

[evert]

Ah, Evert.

Embarrassingly, and weirdly, after a quick measure I only seem to have a 66.5mm stroke. --- I thought I was over 71mm.

I'll double check in the morning and strip the action down again but it looks like I'll have to machine up a custom piston.
Alternatively, perhaps I could use a 99 piston and just replace the body with a 25mm one, depending on the 99 piston's length.



All the best Mick

If my memory is correct, its been stated somewhere that the HW55 has been delivered with different pistons adapted to different power level.
May just be a rumor though, or me remembering something that was said about another gun.

[T 20]

If my memory is correct, its been stated somewhere that the HW55 has been delivered with different pistons adapted to different power level.
May just be a rumor though, or me remembering something that was said about another gun.

I'll definitely be stripping the HW50 action down in the morning as something doesn't add up here after reading this thread :-

https://www.airgunbbs.com/showthread...15#post7990915



Perhaps I measured it wrong this afternoon, though I don't think I did --- very weird.

[T 20]

I'll definitely be stripping the HW50 action down in the morning as something doesn't add up here after reading this thread :-

https://www.airgunbbs.com/showthread...15#post7990915



Perhaps I measured it wrong this afternoon, though I don't think I did --- very weird.

I did measure this wrongly.

After stripping the action this morning I found the stroke to be 69.45mm, this ties in with my prediction of the stroke in the above link, which I missed yesterday.

I will try to have a measuring session over the weekend and then work out the design for a new piston, though it could be that I could extend the stroke on the piston I have.




All the best Mick

[evert]

I did measure this wrongly.

After stripping the action this morning I found the stroke to be 69.45mm, this ties in with my prediction of the stroke in the above link, which I missed yesterday.

I will try to have a measuring session over the weekend and then work out the design for a new piston, though it could be that I could extend the stroke on the piston I have.




All the best Mick

The stroke is somewhat limited by the cylinder in itself. I think you may be able to reach 75mm, but not much more.
And you may probably reach those 75mm's by just trimming the front of the piston.
I'm a bit afraid to take too much off and have the piston coming apart during cocking.

[T 20]

The stroke is somewhat limited by the cylinder in itself. I think you may be able to reach 75mm, but not much more.
And you may probably reach those 75mm's by just trimming the front of the piston.
I'm a bit afraid to take too much off and have the piston coming apart during cocking.

As I started out with a 65mm stroke piston my machining for the TX piston seal is now within 0.5mm of the cross pin hole, so machining the piston face back any further is a none starter strength wise, Evert.

I'm pretty confident that altering a 99 piston could be my best bet --- but if someone could tell me the overall length of a HW99 piston I'd know for sure ?




All the best Mick