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Posted: 6/5/2026 10:10:29 AM EDT
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Painters are painters, gunsmiths are gunsmiths. I take partial responsibility for not ensuring that the instructions "do not coat inside" were written on the work order even though I gave the those instructions verbally to person who took the order. Now I have a beautiful new USGI gas cylinder with a fabulous coating of Cerakote Glacier flat black inside and out. The only part not coated is the threads. A new USGI oprod piston tip will pass inside the cylinder with a slight drag. The technician at Cerakote suggested that the coating should only be 0.001 - 0.002" thick and that it should be okay to just run it as is; due to Glacier's extreme temperature resistance (made for exhaust systems to 1200°) he seemed confident that it would not flake off. He also confirmed that it is harder than bare stainless steel but he could not comment on potential wear on the piston tip. My oprod was recently sent off to Columbus Machine Qorks to have a new piston tip installed to go along with this new gas cylinder. When I called them to discuss this situation they suggested that I send them the gas cylinder so they could check the tolerance between the piston tip and the coated inside of the cylinder. We discussed the possibility of having them machine the inside of the cylinder to remove the coating, but they are also concerned about cutting too deep and beginning to remove metal from the inside of the cylinder. Would you run it as-is if the clearance is okay or would you attempt to remove the Cerakote before reassembling the rifle? |
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I’d run it as-is and just clean way more frequently, until whatever is going to rub off gets rubbed off. (It’s going to happen where the piston tip regularly contacts it). It’ll just get turned into tiny crud with the rest of the carbon fouling. Shouldn’t be a big deal. Just assemble your rifle without the recoil spring, and if it passes the “tilt” test then it should work fine. |
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Thank you very much for your reply - I am definitely considering going in that direction. However, the following information gives me pause when contemplating your comment about "whatever is going to rub off gets rubbed off". I'm wondering which will be wearing down - the coating or the piston tip. 🤔 Attached File |
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Piston tips can be replaced too. I’d run it if the drag was light. Heck it may be a new and unconventional way to rehab a worn gas cylinder. If you get stoppages on the regular then you can revisit the issue. I have seen old machine shop small bore hones but I don’t own one myself. |
The only hyphenated names I like are cartridge names......30-06, 30-40, 38-55 etc.
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Stainless steel is harder than graphite. They might’ve gotten a 5H pencil to leave superficial scratches in stainless steel (or it could simply be graphite transfer onto the steel) but I believe the stainless steel piston tip will easily win the scraping battle. Google AI explains the differences much better than I can… Attached File Difference in testing methodology: Attached File Attached File |
If you think there's a metal part in your gun that is softer than paint, the obvious answer is replace that part with one thats tougher.  The next obvious answer is paint that part. You think somehow the paint is making the parts tougher, so cover the soft metal part with that hard paint. Personally, I'd just wrap some scotchbrite around a socket that fits well into the hole and spin it around with a power tool. 
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