This following is interesting, sort of, or maybe not, depending on the individual.
Back in the 80s I used the Speer 200 grain HP, over 11 grains of Unique in my .45 Colt and the 125 grain Sierra JHP over 18 grains of 2400 with a magnum primer, in my .357. At the time I felt like these were good defense loads, that would perform well given the then current state of bullet technology.
I currently use the Speer 250 grain Gold Dot over 17.5 grains of 2400 in .45 Colt and the 180 grain Nosler Partition HG over 14 grains of H110. While there are other acceptable choices that are currently available, I
personally feel that those are two of the best preforming projectiles currently available.
L to R, Speer 200 grain JHP, Speer 250 grain GD, 125 grain Sierra, 180 grain Nosler HG.
Now the point of my post is, that although
I believe that I'm using the best projectiles currently available in those calibers; would I feel at a great disadvantage, or
under gunned if I were still using the loads I did in the 80s. The answer is no I would not. They are still fully capable of doing what they were intended to do, which is severely wound, kill and/or incapacitate someone.
Also at that time I used the 200 grain SWC, 230 grain FMJ or the Remington 230 grain HP for SD loads in my .45 ACPs, although I now use the 230 grain XTP in my .45 ACPs, I feel the same way about all of those, I would still use them and feel confident.
Round nose lead, full metal jacket and lead semi wadcutter bullets from the past are just as deadly as they ever where, which is very. Like Mike Irwin once opined when someone asked if a .38 Special was still
effective,
'No, nowadays the RNL .38 actually heals people who are shot with it', or something to that effect. You get the idea of what he was trying to convey, of course it is still deadly and effective.
We all want validation and to have our confidence in our chosen defense rounds capabilities bolstered. I wish there were some certain way, to garantee a certain outcome, but there isn't. The simple truth is that despite all the past shootings and all the ballistic testing, there is no precise indicator of exactly how the shooting incident you might be involved in will transpire, or conclude.
tl;dr There are no magic bullets. Bullets of old, or modern, design can work if properly placed.