What caliber of handgun was used to assassinate John Lennon?

A .38 Special handgun was used to assassinate John Lennon.

Mark David Chapman used a Charter Arms Undercover revolver chambered for the .38 Special cartridge. He bought the five-shot weapon in Honolulu on October 27, 1980, before traveling to New York and waiting outside Lennon's residence, The Dakota.

On December 8, 1980, Chapman fired five hollow-point bullets at Lennon as he entered the building. Four struck Lennon in the back, and he was pronounced dead at Roosevelt Hospital at 11:15 p.m. The commonly confused alternatives—.22, .45, and 9mm—are different handgun calibers and were not the ammunition used in the killing. “.38 Special” identifies the cartridge designation, while the revolver itself was made by Charter Arms.