Four Tennessee men face federal firearms charges related to the purchase, trade or sale of as many as 323 guns over the past four years.

Kevin Dawson, 40, of Ooltewah, first came before U.S. Magistrate Judge Susan K. Lee on May 23 to face a criminal complaint that was sent to the federal grand jury for indictment. The grand jury indicted Dawson and three other men Tuesday on charges they conspired to and sold weapons without a federal firearms license and also sold to people prohibited from purchasing weapons.

Dawson, Jack Wardlaw, 65, of Columbia, Tenn., and brothers Carl Monroe, 67, and Richard Monroe, 48, both of Athens, Tenn., face an Aug. 20 trial date on the charges. All except Richard Monroe pleaded not guilty to the charges in Thursday's hearing; Monroe won't enter a plea until he returns to court on July 12 with an attorney.

All four are free on an own recognizance bond awaiting trial.

The original complaint alleged that Dawson sold or traded firearms and ammunition to Jesse Mathews, who police have charged in the April 2, 2011, shooting death of Chattanooga police Sgt. Tim Chapin. Mathews faces the death penalty in a state court trial scheduled for January.

During an arraignment Thursday, Lee spelled out her concerns and the consequences of violating bond conditions to each of the men. Forfeiture information filed in the indictment lists 323 firearms in the possession of the four men.

"Given the number of guns listed, I want to be very clear here," Lee said. "You cannot possess a firearm as of when you leave here."

Lee instructed the men to disclose any firearms they owned or could be associated with them to federal probation officers to avoid any confusion.

Dawson was arrested after police say he tried to purchase a fully automatic Thompson submachine gun, or "Tommy" gun, from an undercover agent with the Bureau of Alcohol, Tobacco, Firearms and Explosives. The complaint outlined gun trades and sales at gun shows in Chattanooga, Knoxville and Nashville.

Jerry Summers represents Wardlaw, Lee Ortwein represents Dawson, Assistant Federal Public Defender Gianna Maio represents Carl Monroe. Richard Monroe told Lee he was in the process of retaining local attorney Mike Caputo. All attorneys declined comment Thursday.

If convicted, Dawson faces a maximum prison sentence of 20 years, Carl Monroe faces 10 years, Richard Monroe and Wardlaw each face up to five years.

Internal Revenue Service investigators along with ATF agents conducted the operation, according to court documents.

Wardlaw, who is Dawson's father-in-law, faces only a single count of conspiracy to sell firearms without a license.

The indictment states that from March 2008 until May 23, 2012, the day of Dawson's arrest, the four men conducted weapons trades and sales of pistols, rifles and assault weapons for cash.

Specifically, Wardlaw is charged with investing at least $15,000 in the "firearms trafficking business" with Dawson in January 2009, according to the indictment.

Prosecutors allege the men made multiple firearms purchases from licensed individuals and businesses in Athens and Lebanon, Tenn. The indictment further alleges Carl Monroe and Dawson both sold or traded firearms to people prohibited from owning weapons. Convicted felons cannot own firearms.

Assistant U.S. Attorney Terra Bay is prosecuting the case against the men but declined to comment.

Attorney Nicholas Foster with the U.S. Trustee's Office in Chattanooga has been assigned as special assistant U.S. attorney for bankruptcy-related charges against Dawson.

The indictment alleges Dawson concealed weapons he owned and money he withdrew while under bankruptcy. The "false entry in a bankruptcy document" charge carries the 20-year maximum sentence.