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pitting on gas cylinder/inner piston ring

RicksOne

RicksOne

.410
I Put 30 rounds of low brass 1200 fps target shells through my Blackie yesterday after installing the MST-930. She fired flawlessly with not one single performance issue.

I took her home and opened her up to wipe it down and inspect everything. My focus was the gas cylinder of course. As suggested I tried to make sure and clean it completely including what looked like caked on carbon build up on the innermost piston ring. After trying to scrape it off I realized it is actually pitting not carbon on that inner piston ring and it appears to have been anodized over. It might have been apart of the cast/mold as it doesn't appear to be rust but I'm not 100% sure about that.

Is this pitting normal? Should I be concerned and contact Mossberg? I'm a little worried about it since this is such an important part of the semi-auto operating system. It certainly did not did not cause any problems in the function but if it is rust I don't want to grow.

Can you guys take a look at yours and tell me if yours has this pitting as well please?

Thanks everyone!

Rick
 


The inner ring has this all the way around it. The outer ring and the piston are both perfect.



As you can see it still shoots just fine but it's still under warranty. Now is the time to do something while I can.
 
So that is pitting and not deposits? I would definitely contact Mossberg about it. The pits themselves shouldn't cause any trouble directly, but the rough surface will collect lots of carbon and could cause issues with the operation of the gas system.
 
Thank you Scotty and everyone else that has helped!

I emailed Joe over @ Maverick Arms today. His auto reply says he's on vacation so am waiting till he gets back.

We were curios about the black anodizing too. A buddy and I have a theory these are anodized black because of this being the "tactical" Blackwater edition. Then laughed about the highly visible bright blue marine spacer tube I recently installed.
 
The wife told me I got a call from Joe on Tuesday. He left me a message apologizing for the delayed response and saying he's going to send out the parts I need. I believe he said the entire gas cylinder piston with rings was on its way. Today I got an email from him with a fed-ex tracking number.

Thank you Joe... and well done Mossberg!
 
Got 2 from fed ex today, I can't wait to get home and put the best one on.

I can't say enough good things about Joe. His quality customer service alone would convince me to buy another Mossberg.
 

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Im gonna try the JM Pro piston. Has anyone ever polished their gas piston?



I used a metal polish on the torn down piston and rings. I even used some on the gas chamber even tho it was painted/blued. I was amazed by how much rust came out of what looked like a very clean gas chamber.
 
I took mine apart and used super high grit sand paper to polish any spots on the piston and rings where the bluing was starting to come off until they were shiney aluminum. I can't say whether it has affected reliability or not because the shotgun has always been very reliable.
 
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