wasn't the reason for 45acp revolvers being issued more due to financial concerns (WWII surplus guns were cheap) more than ballistic concerns (the 32 had been the standard so 38 was already a big step up)?
It's true that the Border Patrol used surplus revolvers because of cost issues. Remember that the 1930's was also the time of the Great Depression that lasted from 1929 to 1940. However the large-bore guns did have advantages in they're particular line of work...
It is interestin to note that when they changed it was the same revolver, but in .38 Special.
Prior to World War One, patrolmen in the larger cities along the east coast wore uniforms similar to what the English Bobbies had popularized. (Also think "Keystone Cops"). When they carried revolvers (and sometimes they didn't) they were usually a small top-break or hand-ejector revolver chambered in .32 S&W Long, .32 Long Colt, or .38 S&W. The prefered method was a hip-pocket holster. By the early 1920's the top-breaks were going out of style and being relaced with Colt or S&W hand-ejectors, sometimes still .32's but more often chambered in .38 S&W (Colt New Police).
After the "Big War" uniform styles changed to along the line of those worn by Army officers, with Sam Browne belts with shoulder straps, and exposed full-flap holsters, often worn cross-draw. At this point you see the introduction of larger .38 Special revolvers as hip-pocket carry becomes obsolete.
Smaller rural departments were far less formal in both uniform styles and choice of sidearms, especially in the South and West.
But I'll quit here, because otherwise I could end up writing a book...
