A couple of things here.
There has been no lowering of the pressure levels for .44 magnum ammo since the round was introduced back in 1956. Pressure is measured differently, that's all. Same ammo all along.
The original 29's used much tougher, heat treated steel than did any other smith revolvers until then. As far as strenth goes, they are every bit as strong as the classic Ruger Super BH. HP White labs proved that many years ago. Both let go at 80,000 psi. The BH in .45 Colt, BTW, let go at 60,000 psi.
What happened to S&W over the years is some of the new owners changed the specs of the 29's. Visible differences are noticed in the lack of pinned barrels and the doing away of the recessed chambers. Other internal differences are not so easily noticed. The so called endurance packages were efforts to redo these design changes.
One more thing. What's safe and at acceptable pressures in one gun may not be so in others. That's one reason why the SAAMI pressure levels are set where they are. If you stick with that, your gun will do fine and last many years.
But if one doesn't strickly follow the loading data put out by the bullet and powder companies, pressures can easily vary, and one has no way to tell just what he's getting in a revolver. E
