I might have the only one on the planet, but the SP101 I bought from son-in-law before he headed for a second tour of Iraq fired .38 wadcutter, .357 140 grain carry loads, 158 grain SWC, and even HOT .357 180 grain JHPs to the same point of aim. I was flabbergasted when I found this out. Not having adjustables had kept me away from the SP, but he needed money and I gave him $250 for it telling him he could buy it back when he gets back. Actually, now, I think I'll take his money and put a couple hundred with it and go out and buy him a new gun and keep this one just because I think I might have the one in a thousand that shoots all my loads to the same POA and, not only that, but I didn't have to even lay a file on the front sight. It shoots STRAIGHT to POA at 25 yards. Needless to say, I'm REAL happy with it.
I'd like to get a 3" version when he buys the gun back, but I'm thinkin' the sight regulation thing is more important than a little more sight radius and the shorter barrel does carry a little better in the thunderwear.
I got nothin' against the 60 other than the hole in the side plate that doesn't do much for me, but the SP101 is a stronger design hands down, by far. I can shoot my 180 grain load in it without worry where I don't feed that load even to K frame guns. It was developed for my Blackhawk, puts up 1306 fps out of my SP101 and is quite accurate, accurate enough to shoot game to 50 yards in fact, this from a snubby! I carry the gun a lot on my walk abouts and stoke it with this round. I'd not want to put it in a lesser gun like the 60 even for occasional use. The SP101 is strong enough to handle it. The round doesn't show any signs of high pressure and the powder charge is within max recommended, but it is so hot, it makes me nervous to shoot it in a non-Ruger. I might just be paranoid, but I don't wanna over-stress a gun of lesser strength. I do like the idea of one of those adjustable sighted M60s with the 5 inch barrel, though, for the back packer. I think that would be an accurate, adequately powerful gun and tote real light on the hip compared to a K frame. In stainless and if you're not in Alaska, it could be the ultimate outdoor/back packer's revolver. I guess you could have an SP101 built with an adjustable sight and a longer barrel, but I can't see Ruger ever offering a comparable revolver to that 5" M60. That gun has always sort of grabbed me even though I don't do much back packing anymore, just little walks on my place or hikes in the woods.