Maybe not to you, but it certainly matters to the revolver we are talking about here.
ltlbear has a very important point, and the one thing that seems to have vectored off from the OPs question is the issue of pressures. Differing velocities don't really mean that much except in the context of how they are affected by pressure. Muzzle velocities are not going to crack frames, pressures in the chambers are. The earlier example of the air force revolvers and their overpressure ammunition; they were "wearing" out frames, or breaking them. There needs to be a lot more information about that for it to have meaning, such as what "wearing" out meant, where breakages occurred and the model of revolver used since the AF experimented with issueing alloy framed airweights and such.
The key here is the pressures that are being created and can the Model 10 handle them. I would have to see some documented proof about heat treating differences and pressure tests to believe that any Model 10 in good condition cannot handle these pressures. I can believe that the cylinder can be an issue, but for instance, the model 10 was adapted to fire 9x19 and .357 Magnum. 9x19 alone, according to SAAMI is in the 35,000 psi range MAP (maximum average pressure), fairly close to .357 magnum (35,000 range, psi); before anyone freaks out over this comment, I have the SAAMI/ANSI pressure rating guide downloaded from their website right in front of me. The .38 spl +P is in the 18,500 range, only 1,500 psi more than standard. If you look at the CUP ratings, they are different numbers, but with comparable results. I've yet to hear about a 547 cracking forcing cones, cylinder walls, etc. There is much discussion about the 13/19/65/66 (etc) cracking forcing cones due to the 125 gr. stuff; I won't resurrect that discussion, but I have always believed it was due to lead bullets leaving deposits and creating pressure in that area. It might be noted that the AF ammuntion cited was 130 gr., I once had a model 1917, and could not see the lead buildup at the mouth of the forcing cone until I got a powerful LED light and magnifying glasses on it. It took me quite a bit of effort to get it out. It made me suspect that this is a culprit when people do not think they have an issue; after posting on a thread about cleaning cylinders, I am certain that many do not understand how to "get the lead out". This would also account for the AFs problems; they used soft lead projectiles for years, and it takes a lot of careful supervision and individual discipline to enforce such cleaning standards. This would also explain why the 547s don't seem to have this problem, yet have such high pressure ratings; you would be hard pressed to find a lead nosed projectile for 9x19, so commonly you are only ever firing copper jacketed rounds, maybe wearing the bore a little more, but leaving a lot less residue to cause back pressure, so for forcing cones, it's a sort of self correcting issue. Same for .357 Magnum, semi-jacketed rounds were the norm when it ruled the day, but lead nosed bullets were for decades the norm for .38 spl.
Are the old loads more powerful than the new? Perhaps, perhaps not. However, I do not see any reason why a Model 10 of any period should not be able to fire +P. I think the +P stamp on modern revolvers is a marketing ploy. Everyone wants power these days, and if they are riding the fence between buying new or old, what a perfect convincer, safety. Of course a new model is safer than a used older one, but let's see some kind of scientific study to prove that 3,000 more PSI will break a model 10, I simply don't believe it. I believe operator headspace and timing is the culprit more than frame strength.
In Germany, all weapons must be proofed by a government proof house with two 25% overcharged rounds. It has always interested me. Incidentally, the Germans also prefer jacketed cartridges, the 9x19 is simply one of them. You can go a long time without having to clean copper deposits, but not so much with lead. That's one (but not all) the military likes jacketed ammuntion, and has for a long time. During WWII, even .38 spl ammunition was jacketed, so it's not just about autos.
End of the story? I woudn't hesitate to fire +P ammuntion through any model 10 that has been maintained and is in good condition, but I would make damn sure that all lead deposits are cleaned out and are always removed after firing. It's a simple concept that I was taught in the area of explosives, less area space in a combustable environment, the more pressure increases.
But that's JMHO.
