Other factors that restricted semi's..
were early political correctness about having a "cocked and locked" firearm in the holster visible to the nervous nellies.
Heck the .357MAG was dissed because it could shoot through and hit innocent bystanders.
Super Vel really broke the ice for reliable feeding and staying where put.
With the advent of the M39 in the mid-fifites and adopted by the INDIANNA State police helped.
Grew up in NE Ohio and hunting buddy need ammo, so we went to local shop he knew it turned out to be the NE Ohio police distributor, it being a Saturday, there were plenty of Cleveland and local PD officers there and they were buying
BHP's @ discount of $250, for off-duty carry. No way they could use for on-duty. This was Mid-70's.
This being after the 1968 HCA, I was able to buy one for that first one would go to my Dad.