There's now two very different "357 Blackhawks" available new.
The standard catalog version is based on a 44Magnum-class frame and is wildly overbuilt for the 357. In my view, the ONLY reasons to go with that is because you're into reloading and want a gun that will be damned hard to kill with a silly mistake, or because you want the convertible version with a second cylinder in 9mm, a factory option on the large-frame. (You can then send the 9mm cylinder off to be converted into something cooler for handloaders, like the 356GNR (41Mag shell necked down to 357) or 357-44Bain&Davis (44Mag shell as a starting point).)
There's also the 50th Anniversary 357 Blackhawk Flattop. A damned good gun, basically an adjustable sight version of the New Vaquero. These "mid frame" guns have shown good quality control and often better out-of-the-box accuracy than their bigger cousins. They're about the same size as a Colt SAA and fit in SAA holsters. The cylinder is still noticeably beefier than a GP100 so while they're small by "Blackhawk" standards they're not at all weak and can cope with large diets of very hot 357s. Best of all, CDNNInvestments has some of the last new 50th 357s for less than $400 brand new. With shipping, taxes, etc. it's still going to be less than $450 out the door which is likely less than a new GP100 for a gun that's stronger and likely to be more accurate.
Upshot: if you're at all interested in a 357 SA, the 50th is a kick-butt deal. You have to call CDNN to confirm prices by phone:
http://www.cdnninvestments.com/
For the record: my Ruger 357 is carried daily as my CCW piece. It's a heavily modified New Vaquero 357. When I bought it in 2005 the 50th 357 was hard to get and more expensive; if I was doing it over I'd use the 50th 357 as a starting point.
In response to this question:
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Interesting. I know people say Ruger DAs are stronger than their SA counterparts (.44 mag Redhawk vs. Blackhawk, for instance), so I wonder: Is a .357 "mid frame" (50th Anniv) BH really stronger than a GP100?
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The answer is "yes".
There's two different aspects to "strength" - "action strength" is the ability to make the gun work properly, keep it's timing intact, stop the cylinder bores at the right point right behind the barrel, etc. The Ruger SAs all have stronger action strength than their DA counterparts - they'll run longer without needing a tune-up.
The Ruger large-frame DAs (Redhawk, SuperRedhawk) have beefier and longer cylinders than the large-frame SAs, so they can cope with hotter ammo and hence have better "blowup resistance" strength (the other kind of strength). The GP100 does NOT have a stronger cylinder than either class of Ruger SA 357 - both the medium and large frame Ruger SAs have beefier cylinders than the GP100.
So both sizes of Ruger factory 357 SAs beat the GP100 in both categories, the medium frame by a little, the large frame SA by one hell of a lot.
Action strength and blowup resistance strength don't always appear in the same gun. A classic example is the S&W 27 and 28 large N-frame 357s. These strongly resist blowing up, however if you load them with light ammo and do a lot of rapid fire, the action parts come unglued. The gun can't handle stopping and starting that heavy cylinder quickly. That's why PPC and other fast-shoot competitions using light loads usually used smaller S&W K-frames as a starting point and then added barrel weights to bring them up to N-frame heft. The smaller Ks were lasting longer than the larger Ns. The Ns could resist blowup, but had weak actions.
Compared to a Ruger SA, *everything* has a weak action, more or less
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