620 mm RHA penetration according to OFB's website. But I don't think that they used this, when they were still testing 3BM-9 APFSDS ammunition. Even if they used the OFB-manufactured recoilless rifle, it is the same as with 3BM-9: It would be a wonder if this old ammunition could penetrate any modern tank. 620 - 650 mm RHA penetration is nothing compared to other, much older, shaped charge ammunition. The HOT missile entered service in 1977 (!) and had an armour penetration of 800 mm RHA. 3BM-9 is weaker than currently existing 100 mm & 105 mm APFSDS!The Round OFB produce has 650mm penetration..
People here see tests against outdated weapon systems which are far below the international standard as proof that the Arjun is as good protected as other modern tanks, but completely ignore that the same weapons wouldn't manage to destroy a mid-1980s T-72.