On the 6 ships I served on the P.O. of the watch carried a Colt 45 auto with 5 rounds in the clip. Asked a Chief Gunners Mate why only 5 rounds in a 7 round magazine. He said they short loaded the magazine to extend the spring life in the magazine.
Admiral Kidd, CINCLANTFLEET Actual, decreed that "all Atlantic Fleet naval personnel would be qualified with the .45 caliber pistol". That was really nuts: we ran completely out of all of our training and most of our war reserve ammo - 5 million rounds - within the month and the qualification percentages were abysmal. I was instructed to devise an abbreviated familiarization course of instruction and did so - and tried it out at the Dam Neck small arms range with a class of 40 average sailors.
Didn't work. Those "average sailors" were horrible shots and I quickly realized that they would have needed far more instruction and many more rounds to become proficient with a .45. My report was not well received but Admiral Kidd finally gave up and took the .45s away from the ensigns on the quarterdecks.
As a post script, I gave the same course to 18 navy wives who were residents of Dam Neck base housing and they were all excellent shots afterward. I have no idea why they were so good and the sailors so awful.