I read one of Agatha Christie's earlier novels last week. The following extracts are quite revealing. From "The Seven Dials Mystery" (1929):
He slipped his hand into the pocket of the dark blue suit into which he had just changed and held out something for Bill's inspection.
'A real, genuine blue-nosed automatic', he said with modest pride.
'No, I say,' said Bill. 'Is it really?' He was undoubtedly impressed.
'Stevens, my man, got him for me. Warranted clean and methodical in his habits. You press the button and Leopold* does the rest'.
* for some unexplained reason, he calls the gun Leopold.
Loraine rose and dressed herself in a tweed coat and skirt. Into one pocket of the coat she dropped an electric torch. Then she opened the drawer of her dressing table and took out a small ivory-handled pistol - almost a toy in appearance. She had bought it the day before at Harrods and she was very pleased with it.
So in 1929, you could buy a gun in a department store. You didn't even have to show up in person - just send your butler to buy it for you. Of course you had to be careful whom you shot.
'I'm glad you didn't shoot', said Jimmy. 'I'm a bit tired of being shot at'.
'I might easily have done so' said Mr Bateman.
'It would be dead against the law if you did', said Jimmy. 'You've got to make quite sure the beggar's house-breaking, you know, before you pot at him. You mustn't jump to conclusions. Otherwise you'd have to explain why you shot a guest on a perfectly innocent errand like mine.'
Luckily we live in more enlightened times when guns are not available to the general public and of course we enjoy far lower levels of crime than they did in 1929. /<sarcasm>