just upgraded my leather HW35 to synthetic...

[Shed tuner]

Understood. But thinking I might try without in the short term and see how it feels, with the longer stroke increasing the SCR and lighter piston maybe reducing the tendency to feel "slammy"?

yeah, it'll help, but a long 3.5mm port is just too big...

[T 20]

We can sort the price and I'll collect at the next Bash if that's okay?

Cheers,

Tone.

Price ? --- It's yours for free, Tone.

[deejayuu]

Great thread so thanks again. Quite excited now 'cos we have one of each leather/synthetic both .177 and corresponding TP differences.
Got to have a play. Seem to remember doing it when the leather version was stuck around 4.5 Ft.lb. and needed jaw void sorting.
need to consult scribbles.

[TonyL]

Price ? --- It's yours for free, Tone.

Mick, you're too kind, thank you.

Do you want the old piston so that you have one to play with and mod?

If so, I'll whip it out before the Bash.

Thanks again, as ever.

[coburn]

You are most welcome to pop down to our club in New Malden one weekend morning and have a quick play mate... I was surprised at the improvement too.

(come via the A3, take the opportunity to get all those cylinders moving )

What? an airgun club in New Malden, How have i missed this?

[old goat]

What? an airgun club in New Malden, How have i missed this?

Been there since 1915

I have lived 5 minutes away for 35 years and only found out about it 4 years ago, walked past it most days.

We also have a RF range

Come along

[Shed tuner]

Been there since 1915

I have lived 5 minutes away for 35 years and only found out about it 4 years ago, walked past it most days.

We also have a RF range

Come along

yup... not quite so long, but for me it's 20 odd years in the area, and only found out a year ago

beware though, most of the members have been there since 1915 too.... it's full of old gits

[coburn]

yup... not quite so long, but for me it's 20 odd years in the area, and only found out a year ago

beware though, most of the members have been there since 1915 too.... it's full of old gits

Sounds like my club, they had to stop bench rest comps, because most were falling asleep

[old goat]

Sounds like my club, they had to stop bench rest comps, because most were falling asleep

You will find we are a considerate club and provide earplugs to minimise the effets of snoring members, they do wake up when Jon turns up with his latest creation, if only to laugh

A young 70 Old Git

All the best

Bob

[Shed tuner]

You will find we are a considerate club and provide earplugs to minimise the effets of snoring members, they do wake up when Jon turns up with his latest creation, if only to laugh

A young 70 Old Git

All the best

Bob

hehehe

[evert]

I measure the stroke and cocking lever gap and do a quick calculation before I start machining.

Then I machine the front of the piston back by the amount needed to end up with a 71mm stroke, naturally this leaves more of the latch rod exposed.

After threading the newly exposed latch rod I screw on an alloy or delrin arbour to take the synthetic seal.

A quick tickle with a Dremel on the rear of the cocking lever slot in the piston to give a 1mm clearance on the cocking lever and it's good to go.

Why do you go for 71mm stroke? What stroke length can be achieved without adjusting the slot in the piston?
I'm a bit concerned about weakening both the piston skirt and the piston rod attachment.

[Shed tuner]

What stroke length can be achieved without adjusting the slot in the piston?
I'm a bit concerned about weakening both the piston skirt and the piston rod attachment.

you need to measure your own rifle mate, there's a bit of variation. mine was around 6mm. just see how much clearance you have from rear edge of cocking shoe, to the piston cocking slot rear edge. Whatever that is, you can increase the stroke by (allowing 2mm for clearance) without any further mods. Then measure the height of an hw 80 seal, compared with the leather nose, and then work out how much metal you need to remove from the piston for it to add up.

Piston still has plenty of engagement with the rod... if worried, just buy a new synth HW piston/seal.

[evert]

Thanks! Measuring is probably (like always) a good idea before I start cutting metal! Just curios to know what other people have found and done.
I've already converted to a synthetic seal, and the rifle is a transitional 1980 gun with a small transfer port.
Buying a new piston is not an option right now, since I've already overspent on airgun parts lately

[T 20]

Why do you go for 71mm stroke? What stroke length can be achieved without adjusting the slot in the piston?
I'm a bit concerned about weakening both the piston skirt and the piston rod attachment.

Sorry for the late reply, evert --- my bad.

71mm just happens to be the longest stroke I found that I can take a HW35 out to without any stock or breech modifications.

When changing a leather sealed piston (having a 65mm stroke) into a synthetic sealed piston (normally a 69mm stroke) I have to chuck the piston up in the lathe to machine it anyway, so it makes sense to machine up to a 71mm stroke while I'm at it.

The HW35 has the same length cylinder as the Old School HW50 which uses the same cocking arm as the 35 and also has a 71mm stroke so there's no issues with the cocking arm at the longer stroke.




All the best Mick

[evert]

Sorry for the late reply, evert --- my bad.

No problem!
I have done the conversion, and machined down the front. The pin that goes through the piston body/front/stem was the determining point for me, didnt want to weaken the surrounding material too much, and left a conservative amount of piston ahead of the pin. Ended up with a 69mm stroke, and had to remove som material at the rear of the piston slot for cocking arm clearance.