HW35 mods?

[randl]

Hi , picked up an old leather sealed HW35 with single sided safety dating from approx 1980 I think ?!
I seem to remember that it’s possible to fit a complete piston with synthetic washer from a later version to help improve the firing cycle. So I’m thinking I will probably do this and also fit tbt spring and guide if he still does them ? ( I’ve been out of airguns for a bit!)
Will also look at possible leaky breach correction .
My main question is do people who have done this conversion feel the outcome has been beneficial?
And secondly is the transfer port left as standard ok with this piston change or does it need altering ? Ps it’s .177 with 19 inch barrel.
Thanks in advance. R

[Phil Russell]

Now I will most likely be shouted down on my views on an old model such as you have, but: why change it?
OK, leaky breach to be mended if it needs it ... really need to chrono and eliminate all other possibilities if the power is way down. No harm in replacing service parts as well if needed.
But then that is only my take on it ... and I can understand your desire to concentrate on the rifle as an instrument and to increase its efficiency rather than as a piece of airgun history as it is.
No idea about Tbt kits. Also no idea on real effects of updating the piston seal other than I believe just doing the seal with no other changes is not really recommended.
Cheers, Phil

[gtfreight]

I replaced the seal with a modern one last summer on my 1965 35 and sleeved the tp from 4mm down to 2.8 and it improved it. Saying that, I had it out last weekend for the first time in a while and it was a bit twangy so I'll be investigating that when I get a moment.

[tinbum]

I prefer the leather seal unmodified in older guns, other don't. I would try a couple first

[CapitalBee]

It might pay to get a measuring stick on the transfer port. I've had a few HW35's from this era and the TP can vary in size, even if a leather seal was fitted. I've had some with 2.8mm TP's and the larger 4mm ports; if it was 4mm, you might want to sleeve it down as Geoff has done, but 2.8mm is a straight swap from a leather sealed piston to the newer synthetic seal version. Don't go the route of the steel replacement adaptor on the old leather seal as it increases piston weight and further reduces the stroke of the piston (reducing the available power). A new piston with synthetic seal will give more stroke (approx 4mm) and lighter piston weight, giving a nicer shot cycle. If your TP is 4mm, I'd be tempted to renovate the leather seal on the original piston tbh as they can run very nicely.

[randl]

Ok thanks guys so far ?
I certainly don’t want to destroy a classic. I owned and an HW35 E back in the late seventies and loved it !
I haven’t shot it yet so can’t actually compare it the 80 and 95 I currently own .
I guess if it feels good after a relube I may leave as is . But I do remember people recommending piston and seal change for a better firing cycle. I certainly won’t be using the synthetic seal adapter for the standard piston.
My thinking was new piston adds a bit of stroke , so less spring needed and hopefully better manners .
I’ll measure the tp when I get a chance , I guess if it’s 4mm then it may stay as is !
Cheers R

[Shed tuner]

https://www.airgunbbs.com/showthread...5-to-synthetic

works great, but you must sleave the port down

[randl]

Thanks Shedtuner, that’s what I remember reading but couldn’t find it again!
If I have to sleeve I might ask for some advice later 😁

[randl]

Hi Guys
I’ve cleaned it up and had a better look it’s actually a .22 I was so pleased to get it yesterday I took it without a proper look !
It’s got 2 arrestor holes and 11mm scope grooves, I was expecting them to be 13mm ?
The serial number is under the barrel and is 8188- -
It’s got a one sided safety.
The transfer port measured roughly with a ruler ! is around 4 mm perhaps a fraction less.

That’s as far as I’ve got at the moment, it’s never been apart and has probably been fired very few times , I know where it came from 😉
It’s pretty caked up with old factory grease , the piston does move after a bit of gentle persuasion.

So do you think it’s a leather seal ? I won’t know until I investigate further.
How does the 4mm port work in .22 with either the leather seal or with the later piston fitted ?
Cheers R

[CapitalBee]

My reaction would be to strip it down replace the breech seal and remove all of the old grease. Whilst apart, re-soak the piston seal in some neatsfoot oil. Re-assemble with fresh grease and see how it shoots. They can shoot very nicely with the old leather piston seal, properly lubricated. The only other thing to consider is the remedial sealing of the cylinder / breech end plug brazing with some Loctite. Not all HW35's had this fault, but whilst apart, you may as well do it ('cause it'll be a pain to strip it all back down again to do it it you find it does have this fault).

[Shed tuner]

yup, do as bee says first.

then if you want it to shoot really nice, buy a new synthetic sealed piston and sleeve down the port. You can't use the 4mm port with the synth seal, it'll be nasty, hence the need to sleeve. But as said, they are not bad in leather.

[randl]

Yes I think that’s a plan 👍
Ill get some neatsfoot and soak the washer .
I’m guessing I lube the rear of the piston and spring etc with moly as usual.
But what about the cylinder does it need anything or is the neatsfoot on the leather seal enough.Never worked on a leather sealed gun like this before.( used to put the odd drop or 2 of abbey sm50 down the transfer port on my old Hw35 e years ago not sure how this is viewed now )

Thanks R

[CapitalBee]

I'd stand the piston upside down in a cap full of neatsfoot overnight. When you remove it, pat off excess oil with kitchen towel, before you insert it into the cylinder, otherwise you'll have rather a lot of shots to burn the excess oil out of the cylinder (and a room full of smoke).

[TonyL]

As per the above.

In terms of "treating" the cylinder, nothing wrong with buffing some moly into the cylinder, too. This could be in the form of dry fine powder, a little paste or some of the aerosol versions in suspension. And, yes, a small smear of moly grease (or tiny smear of moly paste) on the piston tail and some moly grease on the spring and guide will be a good idea. If not already fitted, a top hat would be good, especially with a polished steel washer in front - gives more support to the front of the spring and an extra "bearing" for smoothness - these days a spring without a top hat seems underdressed! I also like to apply moly grease to the circumference of the cylinder once the piston is in and pushed forward and before fitting the spring & guides.

[Shed tuner]

..and don't forget a blob of moly grease on the tail of the piston rod, to lube thru the rear guide and where it latches into the trigger...