I thought Churchill fancied the Thompson in .45. At least that’s what the ad in the magazines shows!
There is a famous picture of Churchill holding a Tommy Gun but I am not sure he ever owned one. I do know he liked Mauser rifles and he also had a Mauser 1896 Broomhandle which his Mother had given him.
He actually used the Broomhandle in the Battle of Omdurman in 1898 I think. He also was in the Boer war but was a correspondent.
Churchill once invited Eisenhower to a shooting match while Eisenhower was visiting Churchill at his home. Churchill won with a very tight group. Eisenhower’s aide a Lieutenant came very close to tying Churchill’s target but Eisenhower didn’t even hit the target.