Hmmm...I always thought the Mark V was THE strongest action, with those nine locking lugs.
Yep, I know. That was the scoop years ago when I bought them.
The thing I remember reading about this is that with so many small lugs (9), they have much smaller bearing surfaces also even though the over-all surface area may be the same or somewhat more than a traditional two-lug gun. Then, when you throw in even small measures of impreciseness in the machining, some of the lugs may not fully mate with their reciprocal surfaces; add some degree of of the bolt or receiver not being fully concentric with the barrel and you may have only 3,4,5 or 6 of those small lugs bearing the brunt of the pressure. Hence, over hundreds or thousands of rounds, set-back can begin to happen.
It is not unusual that a traditional two-lug bolt gun with no squaring and lapping of the lugs will show much more wear on the rearward surface of one lug as opposed to the other after significant use also.
