While there is a chance I am wrong, I doubt the M686 came in a high gloss finish and more than likely it was high polished to be that way. As long as the scratches are minor, they are easily gotten out. If they do not come out with Flitz, then you need to go to the next more aggressive grit (Emory paper or sand paper), then after the scratches are gone, work your way back up to the finer grits and then re-polish with Flitz. Stainless is very forgiving! this is not a hard job and it is a low risk task.
While doing the Flitz and or sand paper route, only go with the grain and I would suggest disassembling the gun so you can make sure no grit or polish gets remains inside (just clean it before reassembly). If you don't know how to disassemble and reassemble, find someone willing to help that is well versed in doing so.
Do not use any power tools. Use a 100% cotton T shirt or a microfiber cloth and only go with the grain. Check work often.