OK. You asked, so I'll try to make a "reasonable" attempt, at explaining MY reasoning, behind it. I don't proclaim to be any sort of smith or gun "expert", but I DO (like to believe that I) know more then your average joe, when it comes to the subject of firearms. So try to keep in mind, that this is merely some crazy old idiot's NON-professional opinion. That shouldn't be very difficult, right? That being said, my "primary" reasoning ISN'T the extra .060 of what you are calling "barrel", that is inside of the action. It is the extra .060 that is OUTSIDE of the action. And I even feel that it is misleading to call it barrel! The way I see it, using that word clouds the mind from seeing it for what it REALLY is. Everyone is free to think what they want I guess, but what I see in that extra .060 is "chamber", not barrel. And, most of the chamber IS outside of the action. Some of the secondary reasons would include: Since the RUMs operate at a higher pressure, going larger maintains the same amount of safety margin, before possible failure might occur. But with the regular shank, some safety margin IS going to be lost. It's like walking that much closer to the cliff that you could fall off of! That fact that they stepped away from standard shank RUMs, very early in the game, along with the major barrel manufacturers shying away from making standard shank RUMS barrels, makes me think that THEY probably had good reasons for doing it. And since THEY pretty much ARE the industry, it only make sense (to me, anyways) to conform to what THEY dictate, if not for compatibility reasons alone. For all intents and purposes, the standard shank RUM is now "wildcat". And wildcat is something that someone like me would probably be best off staying away from. What I mean, is that I'm the sort of individual who doesn't just hotrod guns, I hotrod about everything I own! Don't let this get around, but I think that I just might have the disorder, er wait, let's call it a "condition", that is commonly referred to as "the need for speed". For boys like us, it just might be a smart idea not to play quite so close to the edge, if you know what I mean! If you don't, let me summarize it by saying: I just ain't worth loosing "face" over. I'll list just one more. Then I gotta go. It's getting pretty late around here. Speaking of face, has anyone else heard of the 2 known cases of SS RUM failures. But I'll stay on a positive note here, and just say that the good news, assuming that it really WAS good news, is that both of them did survive!