Originally Posted by
koger
Chatter Marks, I think this is what he is referring to. When a 742 fires the bolt unlocks and travels rearward until it stops, by the recoil spring bottoming out. The bolts locking lugs, which are small and hardened, slide down a rail on the inside of the receiver. When the bolt comes to a stop, The lugs slap the rail somewhat. If the rail is heat treat as it should be, no issues. If not the locking lugs start to hammer, and eventually deform the rail, or cut thru it completely, which causes the bolt head to drop down and lock the action up, causing the gun to jam and neccitating tearing the gun down to get it working, for one shot and then repeat. If it doesnt cut thru, the battering of the rail causes the chatter marks, and slows down the action by the bolt rubbing on them, and dragging the bolt on return, making it unreliable. In my experience, about half of the 742's are like this. I had a gent who had bought one of them new the basket weave addition, and had kept every round of factory ammo shot thru it in the original boxes in his garage. At 152 rounds the rail was eaten thru. I have grown to hate the 742s over the years from working on so many of them. The 740s and had the big one piece lugs on the bolt, and none of the problems with the lugs, hence the reason Remington returned to the same bolt on the 7400. Strangely, the 760 pumps, with the same type bolt and and rail, have none of the problems associated with the 742.