I think an awful lot of the "good old days" factory ammo performance was from a time when very few people had a chronograph ....
... I've never had an 8 3/8" or 8 3/4" revolver and 1930s ammunition to chronograph, but have always wondered if the early 158 @ 1500+ FPS was true. How accurate were the era's chronographs, and how exaggerated might the advertising have been? ...
...The 1500 fps was with an 8 3/8 " barrel . How accurate was a 1935 equivalent of a chronometer? ....
...Pressure barrels and even just a chronograph, that is relatively common today, would have been expensive cutting edge technology only operative by engineers and technicians in the 1930's. How many of those old 1930's - 1950's loading manuals have pressure data included?
That said I have no doubt the big three (Win, Rem, Fed) no longer load 357 Mag all that close to SAAMI Max. That is fairly obvious in the numbers when compared to the results of the boutique loaders like Buffalo Bore and Double Tape and hand loaders that are loading close to that Max. ....
Very early ballistic measurements were made with pendulums, but in the 20th century, prior to the optical sensor chronographs we have today which were invented in the 1950's (under contract to NACA (NASA)), chronographs typically worked by the bullet breaking a series of two wire screens and various mechanisms to record the time interval between the breaks. The first portable version of such a mechanism was invented by a man named Loomis at the Aberdeen Proving Grounds. It used a drum that rotated at a regulated speed to record the interval.
I believe these early ballistic chronographs were capable of good precision but that like automobile engine dynamometers, the details of the testing conditions and protocol could affect the results substantially.
The most practical way to evaluate the ballistics that might have been possible from .357 Magnum in the 1930's would be to use modern equipment. Back then, they would have used Hercules 2400 powder which is very similar if not the same as today's Alliant 2400. It's not practical to prove just how identical they are, but we can be sure that 1930's Hercules 2400 wasn't somehow more similar to H110 in performance results. It might have been different, but it wasn't that much different. There is simply no explanation for how it could have been that much more magnificent back then.
There's also a question of "how much" 2400. We can simply test loads that exceed what we can now accurately measure as a reasonable pressure limit and see how far we would have to go to obtain the historically claimed performance.
Did they get such and such number of feet per second? It doesn't matter because chronographs vary, atmospheric conditions vary, temperatures vary, gun barrels vary, and on and on.
What we will no doubt find is that loads of 2400 even beyond maximum SAAMI specification pressures will not perform as well as loads made with newer powders like H110, Lil'Gun, or Enforcer. The irrefutable truth is that pressure for pressure, we can blow the doors off anything they shot in 1935. Nevertheless, we're realizing more and more that there may not be a good reason to.
There is near-total consensus in the wound ballistics profession that once sufficient expansion and penetration are achieved, adding velocity is mostly ineffective at improving the result. Even if through some inexplicable phenomenon, early 357 Magnum had 100 more fps than today's, there is no reason to believe it would improve results in manstopping and it would not expand the kind of game that could be hunted or the ranges at which the 357 would be effective. It would mostly amount to a difference on paper.
Lastly, Winchester, Remington and Federal are members of SAAMI. Buffalo Bore and Double Tap that are not members of SAAMI. SAAMI's membership list is very clear on their website. Buffalo Bore, Underwood, Double Tap etc. have not obligated themselves to load within SAAMI specifications. Some of their representatives have made claims that they load within SAAMI specification in response to inquiries about that, but they provide no independent verification of this claim. The simplest way for them to do this is unequivocally would be to join SAAMI. SAAMI membership is available to them. If their products are within specification, why don't they join?
Shooting Illustrated published an article about Buffalo Bore ammunition:
"You see, Sundles does a number of things to ensure his ammo is indeed safe. For the Heavy and +P stuff he utilizes ballistic-test labs to confirm pressures, and makes sure it is loaded with consistency, ensuring there are no wide pressure swings. He's careful to post warnings on packaging telling consumers which firearms are safe for the cartridges in the box. Some Buffalo Bore loads may exceed SAAMI specs, but you can rest assured they have been exposed to extensive testing and actual firing in a variety of firearms."
First of all, note that the article indicates some loads may exceed SAAMI specs. Also note that Buffalo Bore is reported to claim they utilize ballistic-test labs to confirm pressures. Will they publish those pressures? Instead, we mostly get non-specific claims that the cartridges are generally safe.
Most gun makers proof test their guns to pressures much higher than SAAMI spec. There is a reasonably wide safety margin above SAAMI spec before the gun blows up. Plenty of handloaders and some ammunition companies take advantage of this. If they can assure there are no "wide pressure swings" and the peak pressures are consistently only so far above SAAMI spec and within the limits of proof loads, they are "generally safe." Handloaders get away with it all the time even if they will nearly all deny that its advisable. For sure, the smarter among them will use firearms with a wider margin than the least.
Now we have to ask, is it worth it? What can we gain from these exceptionally high velocities compared to ammunition produced by SAAMI members or within published load data? The answer is the same as for those 1935 pioneers who may or may not have been shooting a hotter 357. There is simply no reason to believe it was capable of anything that a SAAMI spec 357 can't accomplish. In fact, for several critical applications, a slower 357 is arguably a much better advantage.