As mentioned before L frames are beefed up to handle more full house magnum loads. They will however still shoot loose with very high round counts. The Model 19 and 66 (same thing only stainless) had a problem of shooting loose but also were prone to the forcing cone cracking with bullet weights under 158 grains, which back in the day was 125 and 110 grains. The heavier bullet was easier on the forcing cone but the increased recoil stress was harder on the frame.

There are none of these worries with the GP100 and most other Ruger revolvers, they are like bank vaults. Another tidbit is the cylinder stop notches are also between chambers on a Ruger while S&W puts them centered on the chamber. This results in a much thinner cross section. You really have to watch shooting heavy "magnum'ish" handloads in the big N frame .45s. It's pretty frightening how thin the steel is from the outside wall of the chamber to the centerline of the cylinder stop notch. Ruger has no such affliction. It's not much of an issue except in the .45 Colt and ACP guns, the N frame S&W model 27 & 28 are stout as hell in .357.