AAA glass beads from TIP in Ohio. They just clean the metal with very little abrasion.
If mine, I would have refinished the rifle to AustralianDoD specification by cleaning, blasting and phosphating. Yes, there would be some horrible pitting and some replacement parts but it would be done as original. As mentioned here before, it is what it is. Just my opinion but I have turned quite a few sows ears into silk purses over the years here with nary a complaint other than my own because my arms and hands are shot to Hell from using a bead blast cabinet for almost 30 years!