So before proclaiming the GP-100 the champion of all .357s...
That's a strawman. My comments about the GP100 were rebutting a SINGLE claim, namely that the GP100 wouldn't shoot with a Python or a 586/686. I've not attempted to try to make any sort of a case that would crown any single handgun "champion of all" in any category.
Obviously this test involved only a single sample of each gun, but it did involve quite a variety of loads and all testing was done with a Ransom Rest to eliminate human error.
The problem here is that there are no loads given. What are the bullet types and weights?
I'm not going to type in all the details for each load, but the testing involved 31 loads with bullets ranging from 110gr to 158gr, from Hornady, Speer, Sierra and using 2400, H110, 296 and AA-9 powders with primers from Remington and Federal.
The GP100 turned in 1" groups or smaller with bullets as light as 110gr, but most of the 1" or smaller groups it shot seemed to be with 140 & 158gr bullets.
Interestingly enough, the best groups from the 586 and the Python were also shot with 140gr bullets.
The book I'm quoting from is the "Gun Digest Book of HANDGUN RELOADING" by Dean A. Grennell and Wiley M. Clapp with Ken Howell and Mike Venturino. Published by DBI books, copyright 1987, pages 160-163 show test results from the GP100, the 586 and the Python.
Copies are still available on the used market.
http://www.amazon.com/Gun-Digest-Book-Handgun-Reloading/dp/0873490142
Where the Rugers tended not to fare very well were in 110gr, 125gr JHPs. Ruger views these as self defense rounds and their revolvers do well enough with these for self defense purposes. The tests I've read for years have been pretty consistent in this regard. The Pythons and Smith 686s do better with lighter bullets.
Ok, I'm curious. Ignoring, for the moment, the fact that the testing showed that all of the guns in question were capable of roughly the same level of accuracy regardless of bullet weight, what mechanism is supposed to make the Colt & S&W guns shoot light bullets better than heavy bullets while the Ruger prefers heavy bullets? The only thing I can think of that might have that effect is a rifling twist difference, but from what I've been able to determine, the Colt has a faster twist which would actually mean that, if anything, it would be more likely to shoot better with heavy bullets than the GP100--just the reverse of what you're claiming.
And the S&W 586 uses the same rifling twist as the GP which suggests that there should be little or no difference between the two guns in terms of which weight bullets they shoot best.
Here's another interesting source that also quotes from the same test I've referenced as well as another test.
http://www.thehighroad.org/archive/index.php/t-7712.html
It indicates that Shooting Times did a test indicating that the GP100 and the Python shot within a few hundredths of an inch of each other out to 100 yards--both were only about 0.6" less accurate than the 686 which won that particular test.
In a 1993 Shooting Times article six 357 Magnum revolvers from six different manufacturers were tested with 14 different types of ammo utilizing Ransom Rests and shot at 4 separate distances - 25, 50, 75 , and 100 yards. All were 6" stainless revolvers.
Each revolver was shot 12 times at each distance with each load. When the groups were tabulated for all loads at all distances with each revolver these were the placements for accuracy:
1- 3.28" S&W 686
2- 3.63" Wesson Firearms FB M715
3- 3.75" Taurus M689
4- 3.83" Colt Python
5- 3.87" Ruger GP100
6- 5.08 Rossi M971
In this particular test the difference between the Python and the GP100 was hardly worth mentioning. In fact the first 5 revolvers were all pretty close.
That does not mean that the results will always be the same if a new group of the same guns would go at it again. But, at least in this test , the GP100 held its own.
In another referencer I have on hand - The Gun Digest Book of Handgun Reloading - many handguns of all popular calibers were tested again in the Ransom Rest and the very best group turned in by any gun was by a 4" GP100...
Basically, I don't see any good evidence or rationale for your assertion that the Rugers are designed to shoot better with heavy bullets given their slower twist than Pythons and an identical twist to the 586/686, nor do I see you providing any good evidence that there's a significant difference in accuracy between the Python, the GP100 and the 586. We have one test (at 25 yards) where the GP100 edged the 586 and the Python and a second test (shot at ranges up to 100 yards) where the 586 edged the Python and the GP. However, both tests clearly indicate that the accuracy difference between the 3 guns is minimal, at best.