Taking weight off a hw97 piston

[Rickenbacker]

I think I'm getting confused with the hw95 piston. Think Rooti McNote was refering to me .

Don't fret, I have made worse memory slips myself. Happens to all of us.

[TonyL]

Err. ...you sure about this?
From what I remember about the HW97, it uses all the piston OD, ie over the whole length to guide the piston into the cylinder. ... Piston doesn't have rear bearing like the TX200. Making a step (or two) in the piston OD therefore doesn't sound like a good plan to me. Am I missing something?

BMP01

Actually, no, not sure at all , but it seemed far preferable to do this rather than machine away material from the inside (very difficult and then spring fit issues) or remove some of the rear, as asked by the OP.

Unadventurous me would actually leave it be. The 26mm ones are still very, very nice, and that would also include the 99 and 95. These have slightly lighter Pistons than the 77/97, but also a lower all-up gun weight.

And if I was really intent on improving the later 77/97 (and I'm not saying for one second that they NEED doing), I'd be sourcing a 25mm comp tube and piston, which do come available occasionally.

[ElmerFudd.177]

Right then...

Ive stripped it all down and have cleaned all componants but i have noticed that the cocking lever arm sear/shoe? where it joins the comp tube has what look like stress fractures!
What to do?

I have sanded comp tube, piston and spring ends to a mirror finish.
Stripped the trigger block (that was fun, bloody spacer) thankyou neil180 for your video. Cleaned and sanded all mating surfaces to mirror finish and greased and reassembled and adjustedish

Also put up a 10foot trampolene to keep the kids out of my way. lol.

[Shed tuner]

Ive stripped it all down and have cleaned all componants but i have noticed that the cocking lever arm sear/shoe? where it joins the comp tube has what look like stress fractures!
What to do?

Buy a new one. As this gun had no Anti-bear trap, holding the lever is the only thing saving your fingers if the trigger goes... except it won't work if the cocking arm "horn" breaks off when the trigger lets go...

[seagate]

In all honesty and with greatest respect, unless you've got a machine shop and plenty of spares to wreck and experiment with, maybe you'd be better experimenting with a couple of different springs,a few piston weights and a collection of spring shims. It works for me.

[ElmerFudd.177]

It does have a bear trap, but i understand if the "horn" breaks it wont stop the piston.

Can i not make a new lever? Or wear a thimble on my thumb lol.

[Rickenbacker]

New cocking link required. It's the achilles heel of the 77/97. But you can use a wooden wedge with a screw in it, til the new link arrives.

[Shed tuner]

It does have a bear trap, but i understand if the "horn" breaks it wont stop the piston.

Can i not make a new lever? Or wear a thimble on my thumb lol.

No, it doesn't have a bear trap.

It has a stupid sliding strip of metal that stosp you physically pulling the trigger blade when the lever is down, but this isn't a bear trap - it does nothing if the trigger sear breaks / let's go.

The TX and the LGU (and the FWB300s) DO have beartraps - they act on the cylinders directly and will stop it moving forwards whatever else has going on..

[ElmerFudd.177]

Ok... no beartrap.

Left off anyway (just something to rattle) and if it dont do much.

All greased and put back together...
Tested in the garden and its a different gun a nice thud (even the neighbour said nice)

Went out to zero and check over the crony and its 603fps average with aa field 16 grain which is 12.9fpe or 17.4 joules
Before i start cutting the spring down, will opening the transfer port out to 3.6mm take the power down a little ,alot or not at all? (its currently 3mm)

Accuracy has improved a little i now can get aa field in 16mm groups at 25 meters before it was 20mm i think this maybe that its less hold sensitive maybe

Tried a few out to 50 meters 10 shots and the spread was 48mm ctc

Any help please?

[Shed tuner]

Opening the port out to at least 3.2, probably more like 2.5, will help - but will not reduce the power - almost certainly the opposite.
Before shopping anything, put at least 50 shots through it to settle and re-chrono. If still over then sure, chop off a coil and collapse one.
Also give the barrel a good clean.

[wonky donky]

HW77/97 26mm pistons way too heavy & needs lightening as well as short stroking.

This is what I do, I'm not suggesting anyone else should do it.

A 1/2" slot 110mm long at 120 & 240 degrees is the way to go imo.

If your doing that you may as well machine the nose off first exposing the piston latch rod.

Thread the exposed rod what ever you have to hand, I use 10x1.5

Make yourself a alloy nose to short stroke by 6mm adding a fascility for a front bearing. (Fix the nose using strong threadlock)

Put a goove in the rear of the piston 1/1.5mm from the edge for a rear bearing.

Cut your slots as above.

The rests self explanatory.

The results something LIKE THIS

If you want it lighter remove the sleeve & replace it with alloy.

Hope this helps

[ElmerFudd.177]

Can you drill the transfer port or will this cause fluctuation in power?

I can get to use a lathe to mill it out and was considering to lighten the piston this way too as wonky donkey said

[Dannyboy759]

I used a 25mm LGU piston and put a 77 latch rod in it. Machine down the outside of the body and you can get it to about 220-225g without drilling or machining holes. Plus the fact that its a 25mm piston in a 26mm gun gives you room for nice thick bearings.
If you want to go alloy like has been mentioned these are normally about 170g in venom form and ive copied these myself but you need a strong spring and a larger TP to make the power and they can be very harsh especially in 177, so much so I sold my 177 early venom Lazaglide because it was like a shot gun. not quite but you know what I mean lol

[ElmerFudd.177]

Right then finally chopped a coil off and colapsed one, now shooting at 10.8 fpe much nicer on the cocking and still just a thud in the shoulder.
Not had chance to get any accuracy tests done yet though,

I decided against lightening the piston at this point because i was happy with the firing cycle,

Any pellet preferences out there hw97 in .22??? (Longer barrel then under lever)

As for the barrel checking as on another thread the pellet is quite snug all the way through the barrel...

[Rickenbacker]

The results something LIKE THIS

If you want it lighter remove the sleeve & replace it with alloy.

Hope this helps

Lovely job that is Dave