The problem of case stretching applies more to necked cases than to straight cases. I have had more of a problem with case mouths cracking than stretching. P.O. Ackley designed a number of improved cases that were essentially cyliindrical. It is my understanding that he would show the advantage of the design by removing the locking lugs and firing the rifle. The straight walls of the case clung to the chamber until the pressure dropped and the actions never opened. The comment about rear locking refers to the Winchester Model 94. As Graybeard has noted, the 92, which is a miniature Model 86 action, is very strong. It is more a mid locking action than rear locking. I once tried a series with single cases to see how many loadings they would take before they stretched. I finally got bored and quit before I had the first failure. Now, if you are using a Model 66, 73, or 76, then all bets are off, regardless of how new the gun is. They all have a radically different locing system, that is much weaker.