sb, My results from a single cavity RCBS .530" RB mould are quite similar to yours, i.e., the mean weight was between 222.3 - 224.8 grs.* I'm not sure whether I was bored, but I routinely weigh my RB's, if for no other reason than to eliminate the outliers.
*cast on Thursday (ladle pour); lead thermometer; weighed yesterday.