Two dealers from the gun show in Timonium this past weekend have been charged with selling illegal gun parts.
In Maryland it is illegal to buy or sell magazines that hold more than 20 cartridges.
Police say detectives were working at show this past Friday when they noticed a customer had purchased what appeared to be a large magazine.
They say it turned out to be the 30-round variety.
They seized the magazine, then went to the dealers to buy another one. "The vendor said that he could not say it was a 30-round magazine because he was in Maryland, however the detectives could buy what he was looking for," said Cathy Batton, a spokeswoman for the Baltimore County Police Department.
And that's when police arrested the dealers -- Richard Summers of Waldorf and John Heilmeir of Cumberland, Virginia.
ABC-2 News spoke with John Lamplugh of Appalacian Promotions, which organizes the gun show four times a year at the State Fairgrounds.
He defended the dealers, saying: "It was a 20-round magazine that was pinned. If the pin were removed it would make it a 30-round magazine. They thought it was legal but it wasn't."
We asked Mike Horst of Horst and McCann Firearms in Belair about the "pinning" of magazines. Essentially, it means: "Driving a pin through the body of the magazine such as this one, to make the magazine hold fewer rounds of ammunition," Horst said.
Pin or no pin, Baltimore County police say the capacity to hold 30 rounds makes the magazines illegal to sell.
They seized more than 120 more magazines from Summers and Heilmeir.
Mike Horst says the dealers could have avoided any trouble with the law, by avoiding the state of Maryland altogether.
"What most of my customers do is they'll buy them legally out of state, in a state that does not prohibit 30 round magazines," he said.
This week Governor O'Malley put forward a plan that would further reduce the capacity for magazines sold in Maryland, from 20 rounds to 10.
County police are investigating whether any other 30-round magazines were sold before the two dealers were arrested. Their trials are scheduled to happen this May -- they could face up to three years in jail if they are convicted.
Two men have been arrested and charged for selling illegal firearm magazines at the Timonium gun and Knife Show.
On January 11, detectives arrested John Heilmeier, 57 of Virginia and Richard Summers, 64, of Waldorf for the illegal sales.
An undercover detective observed two customers ask one of the vendors for a magazine for a .223 caliber AR-15 rifle. The vendor sold the customers what appeared to be a 30-round magazine.
Detectives interviewed the customers, confirmed that the magazine was illegal to sell or buy in Maryland and seized the item.
Detectives then went to the same vendor and asked to purchase a 30-round magazine. The vendor told them that they could not say "30-round magazine" because he was in Maryland, but assured the detective that he could buy what he was looking for.
The detective purchased two magazines, which were labeled as holding 20 rounds, but they actually hold 30-rounds. Detectives recovered 121 additional illegal magazines from the stand.
The two were arrested and charged with a firearms violation, and released on their own recognizance.
Charges against the customer who purchased the magazine are pending.
Under current Maryland law, high capacity magazines, over 20-rounds, cannot be sold or purchased.