I think they regularly exceed maximum pressure.
Hahahaha, you should see my garage!
Ammo mfgers buy & produce in huge amounts . Every time propellant lot changes so does charge weight , which is determined by pressure testing . Lot to lot variation is less in " cannister " grade that is sold to reloaders . If you've ever used surplus powder to reload you know it can be substantial . When using such the sage advice of working up loads with any component change becomes even more necessary . If one wants that kind of performance one pays the price . Cast HP's are wonderfully effective if alloy selected is matched to impact velocity & also ductile to not shatter / shed . If you're gonna push 'em gaschecks make life easier . It's much easier to get repeatable bullet performance from jacketed . Cast bullets will deliver exactly what one's willing to invest . Those willing to tailor to fit their use rarely shoot jacketed .
While not the FBI loads from Buffalo Bore, I have a feeling these are probably right stout! I have some 158 grain ammo from the same manufacturer, but it is .357 Magnum.
Buffalo Bore has made a regular routine of shirking SAAMI so there isn’t one good reason to expect that ANY particular Buffalo Bore product aligns with industry standards.
At the same time...
For a modern S&W, the only thing that makes sense from a manufacturing-for-profit standpoint is that their .38 revolvers and their .357 revolvers are made from the same steels and the same heat treating processes.
I am -NOT- advocating that handloaders should load beyond published guidelines. (however, the very skilled and connected those that DO benefit all of us, thank you Mr. Elmer Keith and your contemporaries) But a quality modern firearm can handle the stuff Buffalo Bore makes and can also handle the loads that a skilled handloader develops using established methods to attempt to replicate them.
As to the Blackhawk with a bulged chamber... far too little evidence to come to solid conclusions. A perfectly spec’d load could have bulged that chamber if there was a bore obstruction.
I am curious as to how you know Buffalo Bore routinely exceeds SAAMI spec's.
I am wondering if this is hotter than the FBI load? Knowing the rep of Jurras and the old Super Vel company, I have a feeling it is......
I'd have to look up the data to be sure, but I think CUP pressure on this loads was around 22,000 - 24,000, fifty years ago, according to testing done in the Super Vel lab. They also tested the Norma 110 grain - the hottest .38 Special factory load ever as far as I am aware. It had a pressure of around 27,000. It's important to remember that this was before the +P designation.
At the time, if it said .38 Special on the box, many fired hot factory ammo in any .38 Special revolver. Never heard of one being destroyed, but I'll bet there are a few loose .38 revolvers out there. Refreshingly, it was impossible to ask "Can I fire +P in my gun?" and there were no arguments about doing so either.
Keep in mind that any pressure data that a lab comes up with is only true for that ammo in that pressure testing equipment on that day. It is anybody's guess what the actual pressure is when fired in any particular revolver, and there is no way to test it.