Some 10 years ago or so I tested a .38 Special 158 grain +P load against a 1992 Dodge pickup right front fender. Really it was just preparatory to a test of various .380 ACP and .25 ACP loads and all done just for fun.

Fired from a Model 10 Heavy Barrel, the 158 grain lead SWC slug did penetrate the fender and an inner fender, striking a carefully positioned target disc with force enough to spin it over. Now the discs on that particular homemade target will only flip over, and flip over a single time for +P 158 grain .38 Special loads or 147 grain 9mm loads when squarely struck without an intervening obstruction. No other .38 Special or 9mm loadings, +P or not will manage to do more than set the discs to swinging. The discs pinwheel merrily when struck with .45 ACP, which is what desired by the fellow who made the target. Does it prove a thing? Nope, but I'm not hiding behind automotive sheet metal in an effort to be secure from incoming .38 Special rounds.