I'm thinking about doing this.

It is not really a good idea to nitride barrels after the fact that should honestly be done during the manufacturing process.

Not an LMT barrel but a stainless precision match barrel from Prefered Barrel Blanks. It was first broke in with 200 rounds, then fire lapped with Tubbs Final Finish bullets. Then I hand lapped it before sending it to H&M Metal Processing to have it Nitrided. No adverse effects at all. Rifle is a 6ARC bolt action AR15 that shoots .5" five shot groups @100 yards. Most accurate rifle I own.

http://blacknitride.com/

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It now sports a Billet Uintah lower with a 2 stage Hyperfire trigger. Neat rifle and gets a lot of looks at the range.

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" target="_blank">https://i.imgur.com/XtcoCDx.jpg

It'll be just fine as long as it's cleaned thoroughly if it has been shot already.

Do it, OP. My former coworker is a nitride whore. He's taken a few dozen barrels in to be treated, most of which were shot beforehand. None shot worse after treatment, and now they're better protected against corrosion.