Billings Man Sentenced In Illegal Gun Sales Case

A Billings man with a prior felony conviction has been sentenced to more than four years in federal prison after selling multiple firearms to undercover investigators. According to Acting U.S. Attorney Tim Racicot, 50-year-old Frank Spencer Marr will serve 57 months behind bars, followed by three years of supervised release.

Convicted Felon Pleaded Guilty In 2025

Marr pleaded guilty in July 2025 to being a prohibited person in possession of a firearm and ammunition. Because of his prior conviction for strangling a family member, he was legally barred from having or selling firearms. The case was handled in U.S. District Court under Judge Susan P. Watters.

Undercover Investigation Began With Drug Deal

Court documents show the investigation began in September 2024, when law enforcement conducted an undercover methamphetamine purchase from Marr in Billings. After that deal, Marr offered to sell a handgun, but did not follow through at the time.

Multiple Gun Sales To Undercover Agents

Investigators later reconnected with Marr, leading to a series of controlled firearm purchases. In January 2025, he sold a Glock 10 mm pistol for $400. Weeks later, he offered additional weapons, including what he described as an “Italian 9 mm,” and later an AR-15-style rifle, along with hundreds of rounds of ammunition.

Authorities say a controlled buy later that same day included a semiautomatic rifle and hundreds of rounds of ammunition. Marr continued contacting investigators, claiming he had more guns to sell.

READ MORE: FBI Director Kash Patel in Billings for Public Safety Push

Arrest Made During Final Controlled Buy

The investigation ended on February 27, 2025, when Marr agreed to sell another handgun. An undercover agent picked him up and drove to a meeting location, where the purchase was completed. As the agent exited the vehicle, officers moved in and arrested Marr.

During a later interview, Marr admitted he had possessed one of the firearms for several years.

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Multiple Agencies Involved In Investigation

The case was prosecuted by Assistant U.S. Attorney Jacob Yerger. The investigation involved the ATF, the Montana Division of Criminal Investigation, and the Billings Police Department, all working together to build the case.