We used Muriatic (Brick Cleaning) Acid to "strike" the surface of SS M40A1 Sniper rifle barrels, so they would take the special Black Oxide hot tank "bluing" when we built or rebuilt those rifles at Quantico. We got it as common "Brick cleaning" acid from Hardware stores. Forgive me for adding that on this forum, but I also used it to strip "damascus" shotgun barrels, some dug relics that were of little value and some muzzleloaiding barrels as well. I also used Naval Jelly on some relics and some other barrels.
We had a long plastic trough to hold the Muriatic Acid that we got at a hardware store, it was sold as I think it was either a brick layer's or sheet rock layer's "mud trough." We found we could leave a little oil in the bore and chamber and did not have to plug the bore as long as we did not leave it in the Muriatic Acid more than 20 to 30 seconds and then it was QUICKLY pulled up out of the Acid trough (by the wire through the barrel) and dropped in a another trough holding water right next to it. This method did entirely no harm to the bore and we would have known it had it done so from testing the rifles on the super expensive test racks we had.
When I used Naval Jelly on a couple of “Damascus” shotgun barrels, I found I did not like how quickly it “ate” into the softer iron and left a rough surface. Something to consider if you use it on original iron barrels, perhaps.
I am not a chemist and do not know the relative amount of “acid etching” between Naval Jelly and Brick Layer’s Acid. However from some experience using both of them, I would always try Brick layer’s acid first because you can dilute it by pouring it into water and add more if you need to so it won’t “eat” or etch the surface too much. (Note: NEVER pour water into acid as there is a very fast and very violent reaction that can throw acid all over you.) I would not use either on a barrel unless I was close to a shower or garden hose or at least a large sink, in case you spill some on yourself and can quickly neutralize/wash it off. I can not more strongly suggest one uses the Industrial strength, chemical resistant gloves and a face shield around acid. Even when you are extremely careful around acid, accidents will happen.
Gus