N/A Synthetic/Leather seal Hybrid.

[Sqwirl57]

Im thinking out loud here. Feel free to call me an idiot if I deserve it....

It was recently mentioned that the old leather seals had a slightly gentler shot cycle to them vs the newer synthetic seals used today. Has anyone attempted to stitch (or use of adhesive, maybe both?) a leather seal to the face of a synthetic seal? You'd get the sealing capabilities of synthetic seals with a softer padded face of leather for when the piston slams home with possibly softer shot cycles? You'd lose a bit of swept volume but I can't imagine a whole lot

 

[Mycapt65]

The softer shot cycle doesn't come from the leather being physically softer and landing nicer at the end of it's stroke. It comes from the larger transfer port associated with leather seals. They're larger to compensate for dieseling the accompanies oil soaked piston seals.

Synthetic sealed guns run tighter and should diesel less. They typically use smaller diameter transfer ports to boost peak pressure and reduce lost volume. This chokes the gun. The extra harshness felt over the leather seal gun is the piston bouncing off an air pocket that can't get pushed through the smaller transfer port fast enough.

This is similar to the effect that the same model springer is smoother as caliber increases. As barrel bore diameter increases start pressures decreases and piston bounce declines. This makes the gun more efficient and feel smoother.

You might as well keep you synthetic seal and open the transfer port to reduce piston bounce. If you don't open it too much, it'll likely be smoother. BUT it will make less power. Possibly alot less. If you make it too big the piston will slam. TPs are a dicey thing to experiment with. Making them bigger is easy. Making them smaller? Not so much.

 

[Sqwirl57]

The softer shot cycle doesn't come from the leather being physically softer and landing nicer at the end of it's stroke. It comes from the larger transfer port associated with leather seals. They're larger to compensate for dieseling the accompanies oil soaked piston seals.

Synthetic sealed guns run tighter and should diesel less. They typically use smaller diameter transfer ports to boost peak pressure and reduce lost volume. This chokes the gun. The extra harshness felt over the leather seal gun is the piston bouncing off an air pocket that can't get pushed through the smaller transfer port fast enough.

This is similar to the effect that the same model springer is smoother as caliber increases. As barrel bore diameter increases start pressures decreases and piston bounce declines. This makes the gun more efficient and feel smoother.

You might as well keep you synthetic seal and open the transfer port to reduce piston bounce. If you don't open it too much, it'll likely be smoother. BUT it will make less power. Possibly alot less. If you make it too big the piston will slam. TPs are a dicey thing to experiment with. Making them bigger is easy. Making them smaller? Not so much.

Ok so I understood most of that but what you pointed out about the extra sealing nature of the synthetic creating a higher pressure that the piston can't overcome quite as easily is the logic I was missing.

I'm still wondering if an added cushion to synthetic seal could have some slight benefits. I may play with that

 

[Mycapt65]

The truth is a synthetic sealed piston never slams the end of the compression tube under normal conditions. The smaller transfer port constricts flow enough most guns wouldn't slam if dry fired. The only time a synthetic sealed piston will slam the end of the comp tube is if the seal is completely ruptured.

Here's a picture of a seal from a supposedly professional "Lube tune" 177 R1. It shot like a bucket of bolts. Yet somehow still made 450 fps. I'm not even sure if that train wreck's piston actually slammed the comp tube. However if someone opened up the TP it might have. Luckily the TP was unmolested.

 

[Sqwirl57]

Holy moly lol. That has definitely seen better days. I can understand your point though about it not actually slamming so much

 

[Mycapt65]

Now you see why I'm not a fan of "Lube Tunes".

 

[Sqwirl57]

Now you see why I'm not a fan of "Lube Tunes".

Oh neither am I. I bought a lathe and some other tools specifically so I couldn't completely hack together all of my toys. I do like to experiment some on occasion and thought I may have been onto something with some potential.

 

[MDriskill]

To be clear, a leather piston seal does not have a leather "face" acting as a pad. It's a cup seal with a solid inner filler; only the edges of the seal touch the end of the cylinder. And, as Mycapt65 pointed out, if all is working well the the piston doesn't slam hard into the end anyhow.

Here's a typical leather-sealed piston (Anschutz 335, aka "Crosman Challenger 6500"). Once it all gets worn in, the leather edges will be pretty much flush with the center filler.

 

[Hateful McNasty]

I think a wee bit of slam so to say helps keep the leather "packed" up to the tube wall . Once well " broke in" the air pressure handles that from then out .. ( opinion)