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Discussion Starter · #1 · (Edited)
PSA: Using Sorbo-pads with "cup" style piston heads can cause serious problems.

Using thinner sorbo Pads with "Cup" type piston heads and high powered springs can result in deterioration and deformation of the sorbo pad, and by extension, loss in FPS, barrel blockages, and even complete failure of the action.

The Story:
Earlier this evening there was a break in the poor weather so I took my recently upgraded Type 96 out to zero the scope and hop. Much to my dismay, the rifle was having serious FPS consistency issues. After putting a few more rounds through it, something that looked like the rubber of a hop up bucking flew out the barrel with the BB. After that the rifle wasn't operating properly. The bolt would cycle and lock normally, but the BB's weren't going anywhere. Finally, I opened it up. Sure enough, when I unscrewed the Cylinder head, off came the piston head with it, stuck to the sorbo pad.
As it turns out, the hard plastic of the piston head had warped and shredded the sorbo pad, before finally getting stuck to it. I simply pulled off the pad and cleaned the cylinder head. I wasn't able to find any other instances of this happening so I figured it best I let you guys know in case your gun shows similar problems.

This is how it came out of the Cylinder:

Note the deformation and deterioration of the inside of the sorbo pad:

Scraping off glue and rubber:

All cleaned up. No more sorbo pad for me tho, no more going in all sneaky beaky like.


I'll update this tomorrow once I get a chance to re-chrono and confirm it was the sorbo pad causing the issues.

For reference, I was using the Scatterplot Brand Type 96 Specific 3/16" Sorbo Pad and a guarder precision piston head.
 

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Hmm. To my eye, that style of cylinder head has not enough flat surface to accept a sorbo properly. And that style of cylinder head looks like it will kill a cup seal very quickly too. Just my $0.02.
 

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I should have clarified there isn't sufficient surface area on the cylinder head for a good bond with the sorbo. It needs more flat for the CA adhesive to bond to.
 

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Where did you get the sorbo from? I know that many pads on places like eBay are out of a weak material that breaks apart easily. I personally bought a polyurethane sheet off of McMaster-Carr and cut them myself and they are very durable and dense. (70d) I haven't had one fall apart yet, but they haven't had too much testing. Also, in my MB03 I have a sorbo pad glued on my piston instead and I cut it down to a cone-ish shape and it works pretty well. I believe that pad is only 50d though. If I take it apart later I'll post a picture if I remember to.
 

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I personally bought a polyurethane sheet off of McMaster-Carr and cut them myself and they are very durable and dense.
I'd love to buy stuff from them, but apparently the rules for sending a few bucks worth of plastic are so incredibly difficult that they won't ship outside US.
 

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Discussion Starter · #7 ·
Where did you get the sorbo from?
It was a scatterplot brand pad I got from evike, and I know that those are regarded in most places as being at least standard.

To test whether or not it was in fact the piston head that did it in, I bough a new pad and a Silverback Carbon Fiber piston (review coming soon), and I'll update after my game tomorrow if the pad works alright with that piston.
 

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I'd love to buy stuff from them, but apparently the rules for sending a few bucks worth of plastic are so incredibly difficult that they won't ship outside US.
I'd buy a sheet for you and send it, but the shipping is ridiculous from them. It was around $10 for two 4"x4" sheets.

It was a scatterplot brand pad I got from evike, and I know that those are regarded in most places as being at least standard.

To test whether or not it was in fact the piston head that did it in, I bough a new pad and a Silverback Carbon Fiber piston (review coming soon), and I'll update after my game tomorrow if the pad works alright with that piston.
You can try putting a neoprene pad on top. You can get thin neoprene sheets off of McMaster-Carr as well. If you don't want to use neoprene you can also buy a faucet washer at a hardware store and sand it down to the right size and put that over your sorbo to protect it.
 
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