HW/Weihrauch 35 Leather Piston seal Woes

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harrympope

harrympope

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Jun 28, 2015
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richland Washington
My 1976 35E I stripped apart and the old piston seal was in decent shape but I ordered a spare. The spare showed up a couple of days ago , but I also bought an adapter to use synthetic seals as a back up plan. Trying to get the nut off so I could release the seal was fruitless. And I was careful to grind off the punched dimple locking it in to the stud.I soaked it overnight in Kroil and nothing.I even put some heat on it. I finally had to resort to chucking it in my lathe and turning it off until I got close to the threads where it just fell off. I'm so glad that I ordered the adapter as the cap was rusted to the threaded stud.
To my surprise , I got no more, or no less velocity when I put on a synthetic seal. Velocity was within a couple feet per second, which shows me. That was nothing wrong with the old one.
 
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Mycapt65 said:
No. Your leather sealed gun has a larger transfer port than a synthetic sealed. It will never make the same power with a synthetic seal unless you diesel the crap out of it.
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thx,didn't know that on the port size. Velocity was nearly identical as stated between leather and Synthetic. The point was I thought it would change either up or down and it stayed flat.
 
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harrympope said:
no I didnt. I heard what you needed to do that but what I wanted to do is shoot it see how it breaks first. Is it something I necessarily should do?
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If your seal was sized VERY well you may get away as is on a smooth bore.

But in laymens term, Think of the seal like a windshield wiper blade on the clean windshield .... Chances become it will chatter & squeal due to the the seals lip scraping away all lubricants leaving surface squeaky clean :cautious: .. ever heard a spring piston AG HONK when cocked or fired ?
The Crosshatch surface holds surface lubrication preventing this.
 
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Motorhead said:
If your seal was sized VERY well you may get away as is on a smooth bore.

But in laymens term, Think of the seal like a windshield wiper blade on the clean windshield .... Chances become it will chatter & squeal due to the the seals lip scraping away all lubricants leaving surface squeaky clean :cautious: .. ever heard a spring piston AG HONK when cocked or fired ?
The Crosshatch surface holds surface lubrication preventing this.
Click to expand...
I had one that honked like a dang goose about 30 years ago. I think at that time I put some of Beeman's silicone down the transfer hole and it calmed it down.
 
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Your leather seal Weihrauch has a ~4mm transfer port. Synthetic seal Weihrauchs have a 3.2mm transfer ports. It's my understanding the larger port creates more lost volume and reduces peak pressure.

Leather sealed guns came with larger ports because they required oil that normally dieseled. That dieseling creates higher pressures that contributes to velocity.

The larger port is there to keep dieseling pressure in check. If those pressures got too high the oil would detonate. Detonation loudly cracks like a 22lr and is very bad for the gun and accuracy. This frequently happens when people or manufacturers improperly lube their piston gun.

If your velocity didn't change there probably was something wrong with your leather seal. Because if both seals were working as designed the leather should have made more power in that gun.

If you want more power you should either sleeve the transfer port to ~3.2 mm or go back to a good oiled leather seal.
 
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Mycapt65 said:
Your leather seal Weihrauch has a ~4mm transfer port. Synthetic seal Weihrauchs have a 3.2mm transfer ports. It's my understanding the larger port creates more lost volume and reduces peak pressure.

Leather sealed guns came with larger ports because they required oil that normally dieseled. That dieseling creates higher pressures that contributes to velocity.

The larger port is there to keep dieseling pressure in check. If those pressures got too high the oil would detonate. Detonation loudly cracks like a 22lr and is very bad for the gun and accuracy. This frequently happens when people or manufacturers improperly lube their piston gun.

If your velocity didn't change there probably was something wrong with your leather seal. Because if both seals were working as designed the leather should have made more power in that gun.

If you want more power you should either sleeve the transfer port to ~3.2 mm or go back to a good oiled leather seal.
Click to expand...

I would have preferred to keep the leather seal. But I ruined the end cap and bushing. So I just put the synthetic one on so I could shoot it. I'm going to have to make another end cap and then go back to the leather eventually. Like a dummy I never checked the thread pitch before I put the adapter on. I know it also needs to spring because it's barely shooting 8 fpe. But i'm just shooting off hand indoor And it's a very gentle easy to handle shot cycle.
 
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Tthe leather seals they made were, BETTER, then the solid seals and last longer! they stoped making them with leather as the plastic was cheaper. what i do is..... take out piston and soak the leather seal in leather conditioning oil for about 24 hours. the seal will SWELL and be very tight when reinstalling and seal extremeley well. every couple hundred shots i put 5-6 drops of oil in transfer port and set upright overnight to soak in good. keep them moist and they will last.....FOREVER!
 
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