Older ammo charts showed the standard .38 lead RN load at 860-870 FPS, probably from a six-inch pressure barrel. Modern charts use a vented four-inch pressure barrel, the better to approximate real revolvers in shorter barrel lengths. That accounts for some velocity difference.
Also, a JHP at 925 may well generate more pressure than a LEAD 158 at an "official" 860 FPS, due to the greater drag in the bore (friction) of the jacketed bullet. At best, you're comparing oranges to tangerines.
In the 1960's, I wrote to Fred Miller, then S&W sales chief, and asked him bluntly if I could fire .38-44 ammo in a Model 10. He said that it was safe, but would greatly accelerate wear to the gun, cause unpleasant recoil, and advised that I buy a .38-44 or a .357 if I planned to fire much of that ammo. I think it was sage advice.
That was the true old High Velocity .38-44 round, not modern Plus-P, note.
However, chronographed tests of some modern Plus P do show marked velocity increases over standard speed lead ammo. As a gun writer, I had access to the Federal PR man, and a few years ago, I asked if he'd be kind enough to have an engineer there fire some of their 129 grain Plus P Hydra-Shok ammo in two and three-inch revolvers and let me know the result.
He very kindly undertook that, and reported that there was about an 80-100 fps difference in favor of the longer barrel.
If anyone is interested, I can dig out his letter and confirm the actual velocities.
But even in the snub, the velocity was well over 800FPS; I think about 840 FPS. The three-inch was at 936, if memory serves.
I have seen chrono results printed in the 1960's in which standard lead "service" ammo barely made much over 600 FPS, the gun being a Colt Detective Special. A Chief's Special tried about that time also gave very low velocities, 600-650 FPS. That is over a 200 FPS difference!
That does not suggest that standard loads were then any hotter than now. It could be that longer barrels generated proportionently higher velocity with the powders needing more than a two-inch barrel to get moving. But I'm pretty sure that this wasnt so, as I also saw tests in longer revolvers. The 730 FPS stated by Saxon Pig in this topic is in line with what some of those guns delivered with four-inch barrels. Sometimes,a six-incher would exceed 800FPS, occasionally making 850 FPS. Plus P loads sometimes fire lead bullets beyond 900 FPS in modern four-inch tests.
Tests in six-inch barrels of the former FBI load sometimes reach 1,000FPS.
This is a lead-to-lead comparison. I have scant doubt that modern Plus P is loaded hotter than the old standard velocity, and I think Dr. Pig is comparing JHP to lead bullets and getting a false impression.
Speer Gold Dot 125's often get very close to 900 FPS from even a two-inch barrel. Longer barrels may reach 950 or higher. These are JHP bullets and pressures are almost surely higher than for lead bullets. Bullet weight also differs. Compare that to the 650 FPS speeds of standard lead ammo in snubs in the 1960's!
I do not think that it is unsafe to fire some Plus P ammo in guns made after S&W began marking model numbers in 1957. A statement in Gaylord's, "Handgunner's Guide", published about1960, says that they were by then using a new, improved, stronger steel. But that steel was in use for years before I asked Fred Miller about that .38-44 ammo. I was then in my teens, but recall very vividly what he said about gun wear.
My own policy is that I will fire Plus P if needed, or if that's all that's available if I'm target shooting or plinking. But I won't use it in large quantities for routine practice, as it'll add to wear, and shake loose the small J-frame guns sooner. (However, recent J-frames incorporate better metallurgy, and withstand Plus P better. Model 60's with -4 or higher suffixes are made of improved steels and heat treatment, and are Rated for Plus P use. Still, I don't use it in them
routinely. Certainly, when carrying for defense or animal protection, and for occasional familiarity firing.)
All Ruger .38's are more than ample for Plus P use, including the SP-101. Colt used to advise returning their alloy- framed guns to the factory for examination after firing 1,000 rounds of Plus P. Steel -framed Detective Specials and Police Positive Specials were to be examined after 3,000 rounds. Colt was concerned with the guns shooting loose (cylinder endshake) and with frame stretching.
If the gun's manufacturer makes a statement like that, it tells me that THEY think the ammo is hotter than standard speed used to be.
So, with due respect to Dr. Pig, I think there are too many variables to make a blanket statement that all modern Plus P is no hotter than the old lead service load. Buffalo Bore is certainly hotter than most, on par with those .38-44 velocities of the old days.
I wlll not use Buffalo Bore in any but .38 heavy frame guns (no longer made) and the .357's. In fact, I suspect that it is a fine combat and medium game (coyote, fox, bobcat) load in a K-frame .357 at average ranges. I mean their lead gas check Plus P lead HP.
If had to, I'd fire it in a recent Model 60 for defense or protection from animals. But I prefer milder Plus P ammo for these guns. Speer has some fine examples. And the old basic FBI load is a good one, in most cases, giving excellent penetration. Remington's version has the softest lead, and expands better in short barrels than will the Federal or Winchester versions. From four-inch or longer barrels, all three work well. This was well borne out in trials conducted by the late Steven Camp, and posted on his site. His excellent photos made a fine case for his opinions.
I wish I had a dollar for every post that I and Dr. Pig have made on this board about Plus P ammo. I could buy some of that expensive Buffalo Bore ammo...
More pressure for the same velocity? Is that even possible? If so, what would be the point? 
