When you compare the two, a 4" six shot 686 and a 4" GP-100, the Ruger looks bigger. It's the fullness of that lug... they are the same length. And, the GP-100 weighs in at an ounce more - 41 vs 40 oz. Keep in mind that, as I said before, the Ruger uses cast components, while the older design S&W still employs forged/treated components. I would also look at the 620, the adjustable sight version of the 619 you mentioned. They are the replacements for the 66 models, which have been dropped. They share the 66's partial lug - an aesthetic feature I appreciate, but it also makes for a more easily pointed revolver. With the life of .38 LRN ammo you suggested, any of the listed revolvers would be fine. A 67, or it's fixed sight brethren 64 or 10, would be perfect.
About .38 Specials in a .357 Magnum - they work quite well. Their residue can be easily cleaned - just use a proper gun cleaning solvent and allow time for it to penetrate. A proper bronze bore and cylinder brush would be perfect. As to dissassembly, the most dangerous component in a revolver is a compressed helical spring - like the hammer spring in a GP-100/SRH - and, to a much lessor extent, the trigger return spring in an S&W. While removing the grip and hammer spring & strut is easy in the Ruger, that trigger group can be a bear. Removing the cylinder and yoke from a S&W requires removal of only the front sideplate screw, leaving the cylinder in your hand for detailed cleaning. Removal of the sideplate is easy, should you need to get at the lockwork - and the leaf style hammer spring is pre-loaded by a strain screw, very safe and easy to change. Whichever one you buy, please use the appropriate sized hollow ground screwdriver/bits when removing/replacing screws.
Since they are a personal choice, feel assured that whether you get a GP-100 or a 686 - or the 64/67/619/620, I'll predict you'll find your choice is perfectly fine for .38 plinking... and more! Best of luck.
Stainz
