930 Gas Piston Cleaning
As with any good forum, the more I read, the more knowledge I get. Thanks to all. But today while laying in bed, I was thinking about the 930 Gas System because of a recent FTE (Fail to Eject) thread. And once my mind latches onto something, I just have to go with it until it's settled. So, I pulled my gun apart again and realized that I had neglected something in my previous cleanings. My Gas Piston. That's easy because it seems like it is a part of the barrel itself anyway.
My Gas Piston has three parts. One is the Gas Piston itself, the Gas Piston Outer Ring (the part with a groove that seals against the inside of the barrels gas cylinder assembly, on the barrel itself) and the Seal Ring.
Now before we get any further, does anyone know which Models the seal ring IS used in. The manual says with an * that not all models use the seal ring. Mine does. So, I would think that means that the 930's all use the seal ring. But that's an assumption on my part and not based on any real research.
While checking the entire Gas Piston Assembly, I tried turning the Gas Pistons Outer Ring and although it turned, it wasn't very easy to do. One other thing I noticed. The Outer Ring wear was irregular on the two raised grooves on the outer ring. It was obvious that there was not 100% contact all the way around the inside of the barrels gas cylinder port. Could this be one of those parts that require a "break-in" period to get everything mated and working smoothly? Now I think so. And the thread that talked about polishing the barrels gas cylinder I can see could certainly help too. But polishing the Outer Ring on the gas piston? Hmmm. Making sure it was truely smooth and regular all the way around would be very difficult I think.
And looking at the manuals instructions, the part that grabbed my attention was about excess oil causing carbon buildup in the gas system and may have a negative effect on the firearms performance. I could now see and truly understand how this could be so. Carbon builds up under the Outer Ring and causes it to expand, thereby forcing it outward towards the wall of the barrels gas cylinder and causing binding as an end result. Remember, my gun has run nothing but high power slugs and the problems others have had with low power ammo hasn't crossed my path yet. But it sure would have.
So, the next thing was "How do I really clean this thing?" Well, I could shoot some WD-40 on it. That certainly loosened things up. The outer ring spun easily now. But I couldn't stop there. So, I used a small knife with a thin blade to insert into the cut on the ring to gently expand the ring and allow me to pull it off. The inner Seal Ring came off with it. So, now I had the three parts disassembled and found LOTS of carbon inside the groove that the outer ring clips into. Next came a brass bristle brush and a thorough cleaning ensuring that all carbon was removed. This part I don't even think will get re-oiled because oil will just grab hold of anything that passes by.
From the picture below, you can see the parts disassembled and the irregular wearing on the Outer Ring contact surfaces. I'm sure if I was burning through a few hundred rounds of ammo in a weekend, that wear would be unoticeable. Which is why I made the comment on if this was one of the "break-in" points.
So reassembly is the opposit. Make sure you have the rings assembled where the chamford side face away from the Gas Piston. Make sure the Outer ring spins freely. And your done with this part.
Now lastly, insert the Gas Piston back into the Gas Piston Cylinder on the barrel. It should move freely with no binding. If there is binding, you might want to take some time working it in and out until you feel it move freely. Remember, binding parts are not your friend! Have a great day everyone.
Paul