A myth, at best.
Speer 135 grain 38+P clocks 860+ out of my 2.5" 19-4.
Speer 158 grain 357 clocks 1260+ out of the same gun.
There is a big difference. Regards 18DAI
S&W Model 19 Combat Magnum. Everything you need in a revolver, and nothing you don't.