HW/Weihrauch Hw95 .20 piston seal replacement

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C

camd

Member
Aug 15, 2015
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44
Nsw
Picked up a used 20 cal 95 yesterday in very good condition and came with a few thousand pellets most ftt and a tin of barracudas.
I headed straight to the range and mounted an old nikko stirling I had on another gun and sited in. Barracudas, ftts and jsb all grouped well.
Chronograph showed 7fps variation over 10 shots (699-692) 6 shots were 698.
I noticed it was a little gritty to cock accompanied with a honking noise. Firing cycle very twangy but no loss of sit picture.
Fully stripped the gun degreased an relubed and cocking feels like a completely different gun.
The seal looks worse for wear but is giving really consistent results.

Do I change the seal? If so should I go the red concave seal or green eco seal from custom air seals?

Cheers
1000008764.jpg
 
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Never used a vortex yet but plenty of arh . Lol. Lot a folks like the vortex

????.. ive fitted to if you hold the tube vertical with the piston/seal in at start with a light skin of lube . If I release finger from the port the piston slowly falls ( real slowly to barely sometime you may shake it a bit to help the fall ..lol.) then I plug the port it stops and do this a few times till it bottoms and repeat to check .

Too tight will both you down . Too lose can cause slamming / poor backpressur to control or cushion the piston to a stop .. ( same using loos or poor fit pellets or bad breach seal)

That fit can help get a fps goal as well

It pretty much comes down to read all our advice , get a hand full of seals and go fit up ..

It a experance thing to your personal experience gained that you find works best to any gun ..
 
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The Vortek seals aren't magic, and they benefit from sizing just like any seal does. And I certainly wouldn't spend $72 on one in any circumstance.

The CAS are just fine, I've used them before.

They offer two 26mm seals for your HW95, the Eco seal and the "normal" cup faced seal. I don't know which you have but either will work fine.

The Eco seal will be more forgiving in a bad tube, much like a stock seal, but if it fits well and you put way too much spring behind it you can lose power from thr braking effect of the parachute lip.

The cup seal will need a good tube and proper fitting, but will make the most power under the right conditions.


In your video, id say you are correct that you are not sealing well. Whats strange is that the seal looks to be rubbing on the sides, back where the piston nose fits in it. But there's not much evidence of it sealing on the lip where it should. Ive seen this before on older guns. The piston nose is oversized, and stretches the seal too large at the back. I cant tell exactly from the video, but it looks like it could be an issue in your case.

If it comes back apart, pay close attention to where the seal is contacting the tube. You need the front 1/4 of the seal making contact ideally.

As for seal fit, I'd like a lubed and sized seal to move under index finger pressure down the tube with the port open.

Make sure your breech seal is in good shape too.

Good luck to you, hope you get it fixed.

Screenshot_20240825-091011~2.png
 
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thumper said:
The Vortek seals aren't magic, and they benefit from sizing just like any seal does. And I certainly wouldn't spend $72 on one in any circumstance.

The CAS are just fine, I've used them before.

They offer two 26mm seals for your HW95, the Eco seal and the "normal" cup faced seal. I don't know which you have but either will work fine.

The Eco seal will be more forgiving in a bad tube, much like a stock seal, but if it fits well and you put way too much spring behind it you can lose power from thr braking effect of the parachute lip.

The cup seal will need a good tube and proper fitting, but will make the most power under the right conditions.


In your video, id say you are correct that you are not sealing well. Whats strange is that the seal looks to be rubbing on the sides, back where the piston nose fits in it. But there's not much evidence of it sealing on the lip where it should. Ive seen this before on older guns. The piston nose is oversized, and stretches the seal too large at the back. I cant tell exactly from the video, but it looks like it could be an issue in your case.

If it comes back apart, pay close attention to where the seal is contacting the tube. You need the front 1/4 of the seal making contact ideally.

As for seal fit, I'd like a lubed and sized seal to move under index finger pressure down the tube with the port open.

Make sure your breech seal is in good shape too.

Good luck to you, hope you get it fixed.

View attachment 491003
Click to expand...
Mate you are correct, the seal was a tight fit to the piston button and slightly buldged the seal.
thumper said:
The Vortek seals aren't magic, and they benefit from sizing just like any seal does. And I certainly wouldn't spend $72 on one in any circumstance.

The CAS are just fine, I've used them before.

They offer two 26mm seals for your HW95, the Eco seal and the "normal" cup faced seal. I don't know which you have but either will work fine.

The Eco seal will be more forgiving in a bad tube, much like a stock seal, but if it fits well and you put way too much spring behind it you can lose power from thr braking effect of the parachute lip.

The cup seal will need a good tube and proper fitting, but will make the most power under the right conditions.


In your video, id say you are correct that you are not sealing well. Whats strange is that the seal looks to be rubbing on the sides, back where the piston nose fits in it. But there's not much evidence of it sealing on the lip where it should. Ive seen this before on older guns. The piston nose is oversized, and stretches the seal too large at the back. I cant tell exactly from the video, but it looks like it could be an issue in your case.

If it comes back apart, pay close attention to where the seal is contacting the tube. You need the front 1/4 of the seal making contact ideally.

As for seal fit, I'd like a lubed and sized seal to move under index finger pressure down the tube with the port open.

Make sure your breech seal is in good shape too.

Good luck to you, hope you get it fixed.

View attachment 491003
Click to expand...
Your are right! When fitting the seal was a tight fit to the piston button, causing a slight buldge. Initially when I test fitted I was getting a good seal. Shot cycle after a few shots was slammy (disassembly shows evidence of this).
 
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crowski said:
I’m not an expert but I listened to all the expert advice on this forum. The Vortek piston seal won my vote.View attachment 490980Getting ready for the changeover. Crow
Click to expand...
Was my first option... but couldn't justify the shipping cost. My mate may be getting a vortek kit, I'll see if he can put some extra seal in his order 😊
 
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I have used ARH and Vortek. In my Beeman R9 .22 it worked very well, but you have to be patient with this seal, because it actually conforms to the cylinder, so shoot at least 500 pellets before you decide to try to "size it down", like you would with and ARH seal. I also have a Vortek seal in a Diana 34 classic. I shot around 400 rounds through it before I chrono graphed again, and I could literally see a couple of FPS increase every 10 shots as the seal was still settling in.
 
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