The 2A and 2A1 rifles which I have owned and handled have ALL been new built 7.62 actions.
The difference between the 2 rifles is the rear sight tanget on a 2A is a .303 (1800 or 2000?? yards) tangent leaf on a recalibrated bed.
The 2A1 has a new sight bed and tangent leaf.
Numrich at one point had loose 2A/2A1 7.62 barrels for sale - who knkws what they have been fitted to.
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I would think that the "Proof Master" would have an idea of whether actions failed proof or not.
I believe that comment was circa 1962/63ish and either in the Reynolds book or American Rifleman magazine.
This would correspond with the start of 2A production.