BC, on the older guns the rail that runs along the side of the receiver near the back at the point where the bolt head stops. At this point the bolt head will over rotate and dig into the rail. When its closed look through the slot that the bolt handle slides through. Or just take out the trigger assembly.

On the 7400's it takes many many many more rounds fired but look at the top of the receiver where the lugs slide through and also along the same rail as the older versions (it will be smaller).

At 500 rounds you will probably not see anything especially if you have a newer 7400. The older 740's and 742's are far worse with this problem.


The next one I have come in that is real bad I will hopefully remember to take a pic and post it for you.