Chinaka Adoezuwe, 26, was killed after instructing the man to shoot him as he was wearing the charms around his neck.
Police in the country's south-eastern Imo state say the client has been arrested on suspicion of murder.
Charms are popular in Nigeria, where traditional healers are consulted for cures for various ailments.
But there have been several reports of people being killed after testing "bullet-proof" charms and medicines.
"A young man had gone to [the healer] to prepare bullet-proof charms for him, which the native doctor did," a villager told the Punch newspaper.
"To prove the efficacy of the new charms, [he] positioned and handed over a gun to his customer. Tragedy struck."
In January, a traditional medicine seller was arrested after a man drank a "bullet-repelling" liquid and was shot dead.
The seller in north-western Nigeria reportedly assured the man that he could not die if he was shot.