With the approval of the Transportation Security Administration, manufacturer Sig Sauer released specifics of the weapons in a press release, ABC News reported Wednesday.
Sig Sauer has a contract to equip air marshals with its .357 SIG caliber P250 Compact pistol, ABC said.
Current and former Air Marshals called the release part of "an alarming pattern of disclosures" by the TSA.
"This is the last thing you want to give to anyone who wants to carry out an act of terror," said Frank Terreri, president of a trade group representing the marshals.
"Anyone who wants to take over a plane can be proactive and research that type of weapon, basically know everything about that weapon before going on the plane," he said. "You really don't want to give that playbook out to your enemy."
The air marshals approved the information released, a Sig Sauer spokesman said.
"They changed it slightly, but there was no sensitive information in it," said Bud Fini, vice president for marketing at Sig Sauer. "I don't think it's that big of a deal."
The disclosure closely follows another security breach involving the TSA, which released an improperly edited manual online revealing confidential data about air passenger screening, ABC said.