IMHO: Marshall and Sanow are bogus. There are too many variables involved for anyone to look at street records and say, "This caliber in this weight is tops!"

Book Review: Handgun Stopping Power - The Definitive Study

Nor is looking at 100 year records worth much. The ammo available now is vastly superior to what what available 100 years ago.

The 45 vs 38 thing came from the Moro war. That pitted a .38 Long Colt against the 45 acp. It used a 150 grain bullet moving at 770 fps with roughly 200 ft lbs of energy. Also, "Colt retained the single-diameter charge hole, so the bullet was grossly undersize as it traveled through the chamber throat. It was supposed to expand in the throat and be "swaged down," or reduced again in diameter, as it entered the barrel, but expanded unevenly producing poor accuracy."

.38 Long Colt - Wikipedia, the free encyclopedia

So a low quality bullet from a poorly designed gun with 200 ft/lbs of energy is not comparable to a very well designed bullet like Buffalo Bore uses in 38+P, with a 158 grain bullet moving at 1000 fps and 350 ft lbs of energy. Buffalo Bore says "This bullet will mushroom violently on impact and will penetrate roughly 14 inches in human flesh." I don't doubt them. Their regular .38, non +p ammo gives 14 inches, with smaller diameter:

Buffalo Bore 158gr (non +P) SWC-HC

Buffalo Bore 125gr Speer Low Velocity JHC

And 14 inches of penetration (and 350 ft/lbs) is a couple of inches greater penetration than a .45ACP Speer Gold Dot 200gr + provided:

200 grain Speer Gold Dot +P

while providing almost as much energy.

Would I prefer a 45 acp over a regular pressure 38? Yes. The 38 ammo above gave 235 ft lbs vs 350 for +p, and is at the bottom end of what I would consider acceptable self defense ammo - all other things being equal.

Also, manufacturers now do a much better job of matching bullet construction to power. They don't use hard bullets with low power, or soft bullets with high power. Their ammo is tested in normal sized guns (no 8" standard), and will perform more consistently than 38 ammo from Elmer Keith's day.

If anyone knows of any scientific data that shows a 45 acp outperforms a 38+P at self defense, I'd love to see it. Hunters are probably the best source of information on caliber effectiveness, and I'm sure most would prefer 45 acp to 38+P - but I'd love to see some side by side comparisons!

If I limit myself to the 60LS, I use Buffalo Bore's 38+P. For my 686+, I use 357 ammo at medium power. If I carry my Ruger Alaskan, it has 44 mag ammo in it - but I've seen no evidence it will stop anyone any better than a good 38+P. My guess is that it would, IF I shoot it with equal accuracy and hit the same spot. Big if, in my case.

And no, using +P ammo in modern guns won't hurt them. With modern guns and modern ammo, a good rule of thumb is that if your hand can handle it, so will the gun. Of course, if you carry an 1890 production .38 Long Colt...well, then it is time to switch to a .45!

Also, I'm not in any way slamming the 45 acp. It has a big bullet giving good penetration with moderate recoil - what is not to like? But in a revolver, it comes at the cost of size. I'd LOVE for someone to make a 686/Ruger GP100 5 shot in 45 acp...but I'm still waiting.