Discounting the broken stocks which are a different level of failure that metal failures, looks to me like the issue was that guns got knocked off face and then the locking bolts were trying to carry the whole load - a job for which they are not suited. There doesn't seem to be any indication that the M-21 came off face. Wonder why?? Is the M-21 action strong and durable? Yes! Is the whole gun somehow extra strong? No - same stock problems as others and the same barrel/rib solder problems. Again, looks to me like at least one of the competition would have run a refutation if the test was entirely bogus.
