Hey guys. First time poster here. I recently was given a M&P15 Sport II as a gift, and it is my first AR. I've been a pistol guy up until now, and in the past, I've used Shooter's Choice Rust Prevent Corrosion Inhibitor on my guns. I was just wondering if this product is safe for use on the Armornite finish on the barrel.

No problem.
Armornite is really a heat treat process, not a traditional finish.
Welcome to the Forum.
Jim