When I started in the late 70's, new officers primarily walked a "beat". With few exceptions, our feet did not see the inside of a car the first year or two. During that time I carried a nickel finished S & W Model 27, 6 inch revolver in a Safariland swivel holster with a thumbsnap. I recall that it had a snap that kept it from moving fore and aft while walking. On those occasions when you were in the car, the swivel was unsnapped and you could rotate the bottom of the holster forward for ease while sitting. I carried a Safariland Model 78HV dump pouch. The plastic liners were removed which permitted me to utilize two Bianchi Speed Strips which held an additional twelve rounds
When I went to my second and last department, patrol was primarily by vehicle and I opted for a Safariland Border Patrol holster for my Model 15 and eventually Model 66 and Model 686. These three remaining revolvers had 4 inch barrels.
As an aside, I opted for the 6 inch barrel because, back then, .357 magnums utilized slow-burning powders. The longer barrel served to more completely burn these powders resulting in less "flash", blast, and un-burned powder granules beneath the extractor star. Over the years with advances in smokeless powder and bullets, I see this now as a non-issue.
JM2C