Winchester 1400/140 o ring

[10-Ring]

I had an inoperable Winchester Ranger 140 in 20ga given to me.  I disassembled, cleaned, and reassembled it.  The last person who assembled it failed to install the firing pin correctly, preventing the gun from going into battery.  No secret that the 140s are junk guns, but the price was right and it would make a good boat, 4 wheeler, tractor, wife gun. 

To the point: The gun fails to eject the spent shell.  I think that the ejector and the extractor are fine as they work like expected when manually operating the bolt.  Looking at the schematic for the gun I see an "o ring forearm spacer" but can't figure out exactly where it should go.  The best I can tell doing internet research there are no o rings on the piston cup, which doesn't really make sense to me.  Does anyone happen to have a 1400 or 140 that they may be able to show me where this o ring is located exactly?  Also measurements of the o ring would be awesome.  At $18 for a new one in going to try to fit a generic to it. 

[quedz]

https://www.trapshooters.com/threads/winchester-1400-mk2-help.229455/page-2

https://www.midwestgunworks.com/winchester-1400-1500/parts.html?page=2#/perpage:48

Edited April 30, 2019 by hughd

[10-Ring]

Update: HughD, if you look at that link that you posted from Midwest gun works, part number 6 is what I was inquiring about.  That o-ring was going to cost me about $18 shipped. Not wanting to put that kind of money into a free gun that I really have not figured out what I'm going to use for, I made a gasket out of three layers of duct tape. It's working great now!