Kevin,
According to the 1997 DGW Catalog, your Rifle resembles a Zouave Rifle without the patch box... 12,501 were made by Remington - but none were issued. The sights look to be correct...
The only Artillery ML Firearm I can find is the Dixie J.P. Murray Carbine, and it was made with a 23-1/2 inch tapered barrel.
Question? / Thought?
I would assume that your rifle (when new) would have come in the "white" - (the barrel not blued). It almost looks to me like someone stripped the bluing off your rifle barrel... Perhaps even used something to pit the exterior of the barrel.
I hope I'm wrong - and I certainly hope you didn't get taken on this purchase... That lock just looks way to pristine to be that clear on the inside with (for lack of better wording) no signs of usage. I don't even see a wear spot on the sear.