The "secret non-cannister powders not available to handloaders producing unheard of results" bugaboo is a common sales pitch. If it actually existed and was so awesome, the powder companies would be more than happy to sell it to eager handloading customers. In fact, they'd be selling a helluva lot more of it to the thousands of handloaders than a single boutique ammo maker.

Fact is, the laws of pressure and performance aren't magically suspended at the Buffalo Bore factory. Note that no hard pressure specs are given for the ammunition. That +P Buffalo Bore ammo is most likely loaded beyond SAAMI spec for .38 Special +P. To get 1000+ fps from a 2" J frame with a 158 grain lead bullet, the level being loaded is +P+: which is to say, well beyond 18,500 cup, akin to the .38/44 ammo of yesteryear (22,000-28,000). IIRC, a shooter previously send some particular super-awesome BB ammo to get pressure tested and the results were well over SAAMI spec, but I'd have to do a more extensive search to find the details.

A modern good condition revolver shouldn't explode at that level. S&W makes .357 magnum guns on the J frame that are only marginally different in construction than the .38 models. But an older gun - or an aluminum alloy frame gun - can get stretched and distorted with that kind of ammo, and becomes unreliable and unsafe. How much of that ammo will do that is a good question - alloy J frame .38s have been know to be rendered useless with as little as 4 boxes of that kind of pressure ammo.

Folks seeking the best performance should know that you cannot turn a .38 calibre weapon into a magical death ray, and indeed there are too many variables involved to create 100% effective "one-shot manstopper" with any calibre you can carry on your person. Better advice in my view is to select a load which you can shoot in sufficient quantity to become proficient with in the gun you actually use, which means a reliable load that shoots to POA and will not beat you or the firearm into oblivion. There is really not much difference in terminal effect amongst the various .38 loadings, so long as it penetrates sufficiently. But we all want that magic bullet.

In my experience the shooter armed with, for example, .38 wadcutters who can place them accurately and quickly on one and more targets, is better armed than the person relying on a heavy load that cannot be shot well, or quickly, or that causes the weapon to be unreliable.