Blackhawk you are correct and no offence taken. I believe it was the fact that he lashed it down that cracked the stock. I was not present when it was done, just informed of the process after the fact. He was an acquaintance and wanted to buy the rifle or have one made by Remington and I had just purchase another rifle in the same caliber I liked better and owned a sister to it in 300 WM, so I loaned him mine to try. I don't know what his thought process was. I think he thought he was going to make it shoot in the same hole by doing so, I cannot say for sure. That particular rifle as best I remember only weighed about 7 or 8 pounds scoped, but recoil was easy on the shoulder even with 156 grain loads. He may have feared it, though. I don't know what was going on in his head and I didn't ask I simple took the rifle back and had it fixed. I use several Caldwell bags I just don't care from the lead sled. Though, as has been mentioned, I can see there usefulness for someone who is having to test and shoot multiple rifles in a single day.
As to the integrity of the stock if memory serves me correctly those stocks were either HS percision or McMillian and while it is possible there could have been a preexisting problem it is doubtful. The gun shot consistent 5 and 10 shot groups that were well within sub moa. I have owed multiple guns with those stocks and never had an issue. The stock cracked just in front of the trigger guard right were you would expect it to. That is the weakest point on any rifle. It is the place where all the energy is transfered back to if the rifle is not allowed to recoil in some way.
One other note on the subject. That particular stock was glass bedded and built before the wide spread advent of the aluminum chassis. Thus, the issue is probably most likely to occur, as is evidenced by most on here who have experienced such failures, on older rifles, pre 1999. If the rifles you are shooting are chassis guns or have aluminum bedding blocks you should be fine. The same could be said for newer high end scopes verses some of their older siblings as many of them are made to take the recoil of modern high powered air guns and 50 BMG's, which are considerably harsher on them than any hunting rifle. The lead sled has it place, it is just not for me.
Happy hunting my friend and blessings!