Can you explain the pinned aspect?
Since M700 lugs are a separate "collar" arrangement, they can tend to spin just a hair when you tighten the barrel down, taking them out of plumb (straight down below the center of the barrel). Frustrating, and if off too far, could lock it into a glass bedding job.
The pins are drilled into the face of the receiver, and go into corresponding little holes in the lug. Prevents them from moving.
Handy, but they require precision drilling (don't do it with a handheld drill). They also make a nifty little jig that will hold it, or as most do, just scribe a small witness mark, and give it a try or two till the barrel snugs down and the lug is exactly where you want it.
