Thanks I used a polishing kit that attaches to a bench grinder. 3 different grade mops and 2 grades of compound.
I stripped the mags first then removed the blueing/coating with the coarse mop and then moved on to the finer ones once it had all gone. There are a few hard to get angles but if you keep at it you can get it all off. It took me around 2hrs to do the barrel, take down leaver and 2 mags.
The mags feed so much better in the mag well too.