AEA Bintac S45 .357 valve pin issue

Apex

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Aug 19, 2025
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Hi all.
I bought a pre-owned S45, for cheap with a air leak from the barrel.
The previous owner told me that it needs a new valve pin, so i changed the pin but it,s still leaking and shooting in full auto mode.
I noticed that there is no valve seat inside the housing, is that normal for this type of gun ?
The valve pin is now closing against the bare metal from the housing .
 
Hi all.
I bought a pre-owned S45, for cheap with a air leak from the barrel.
The previous owner told me that it needs a new valve pin, so i changed the pin but it,s still leaking and shooting in full auto mode.
I noticed that there is no valve seat inside the housing, is that normal for this type of gun ?
The valve pin is now closing against the bare metal from the housing .
That stinks, I have the .357 in 13", but I haven't done anything except tighten up the bolt/ firing mechanism, and upgrade the front tank. There are some good valve pin videos on YouTube. Have you tried calling bintac? They usually have valve pin kits as well
 
The valve pin sits in a little metal cup housing that threads into the receiver part, there's an oring on the outside that seals from housing to receiver and one inside that seals from the valve pin to the housing. Those are the orings I'd look at first, but if the gun is leaking and you bought it used, might as well tear out and replace all the orings on the gun imo. Don't shoot below 3000psi to give the bolt enough force to catch the sear.