I do not have /4C in front of me but here is the information. Hopefully this will help. AMS specifications are in inches, feet ..etc. So any conversion to metric are approxment. Does this corraspond with /4C? If so, then it is the same as 2430 and all the 2431/ specifications for steel media.
1" X 1" = 1 sq in or 25.4mm X 25.4mm = 645 sq mm
1/2" X 1/2" = .25 sq in or 12.7mm X 12.7mm = 151 sq mm
1/4" X 1/4" = .065 sq in. or 6.32mm X 6.32mm = 40 sq mm
Whether this method is bias or not, the question that needs to be asked is; does it control the process either manufacturing or peening to produce a desired result? I believe this test method has been in place for decades and has been proven. But, that does not mean that a proposal to the committee for a better method should not be considered. Please feel free to make that proposal and if not already become a member of the committee.
I hope this helps.
