A Utah man claimed he was not guilty of manufacturing a part that turns a regular AR-15 rifle into a fully automatic weapon. Whatever the buyer does with the small piece of aluminum is on them, he argued.

“Once the kit is sold, whose responsibility is it to make sure it stays within the confines of the law?” Scott Ray Bishop asked the federal court jury during his closing arguments Friday.

But the jury, about an hour later, found Bishop guilty as charged of one count each of unlawfully engaging in the business of manufacturing machine guns and illegal possession of machine guns from 2013 to 2016.

He now faces a maximum punishment for each crime of 10 years in prison and a $250,000 fine. He will be sentenced March 22.

Bishop, who was on release pending the outcome of the trial, will be allowed to remain free until the sentencing.

A nonlawyer, Bishop represented himself during a four-day trial in U.S. District Court in Salt Lake City that wrapped up Friday.

Federal prosecutors claimed Bishop sold 1,400 of these kits throughout the country from 2013 to 2016 for $100 each. The kit included a piece of metal that could be placed in the lower receiver of the assault-style rifles to allow the gun to continually fire while the trigger was pressed down.

“Mr. Bishop flooded our country with illegal machine guns,” Assistant U.S. Attorney J. Drew Yeates told the jury. “Find him guilty.”

The Bureau of Alcohol, Tobacco, Firearms and Explosives caught wind of the sales, which Bishop was making through his website, and searched his mobile home in American Fork. They seized evidence and told Bishop they believed he was manufacturing machine guns. Under federal law, the making of parts that turns a gun into a machine gun is equal to making a machine gun.

But Bishop contends a fully automatic weapon isn’t defined as a machine gun under the law.

However, an undercover ATF agent contacted Bishop to ask about getting a fully automatic weapon. Bishop allegedly said making or possessing an automatic is “not legal,” but added, “I’m not real concerned about that.”

During the February 2016 transaction, the agent asked how to convert semiautomatic rifles into automatic weapons and Bishop allegedly admitted he possessed automatic firearms. He also admitted his actions were not legal and said that “the laws that are on the books are a bunch of bull----,” according to testimony.

Bishop presented his case Friday, which consisted of testimony from himself and a friend of his. But the process was disjointed, with Bishop requesting several breaks to confer with his standby attorney, who was hidden from the jury at Bishop’s request.

Bishop attempted to give expert testimony on the technicalities of his gun modifications, without being approved as an expert witness. He asked to show the jury photos and videos, but didn’t want the scrutiny of admitting them into evidence.

Bishop was attempting to bring forth an argument that his modification was similar to a bump stock, something mostly known only to gun enthusiasts but hit the national media after being allegedly used in the largest mass shooting in U.S. history in Last Vegas in October.

Bump stocks under current law are legal. If Bishop could show the similarities between that device and his own modification, he would have an interesting defense, U.S. District Judge Dee Benson said.

But Benson ruled the bulk of Bishop’s argument — a “bombshell of evidence” as Benson called it — required an expert witness to verify. However, Bishop was bringing it up for the first time. He had never made the point to investigators or during opening arguments. Even if he were allowed to discuss the technicalities of it, the prosecution would be at a disadvantage on rebuttal.

“I don’t know why you get some special break or opportunity to surprise them with this,” Benson said.

Following a subsequent break, Bishop asked for a mistrial, saying his constitutional right to defend himself was being infringed upon. The request was promptly denied.

Bishop then presented a defense that his product was for educational and informational purposes only, and that the instructions mailed out with the kit specifically outline what not to do — complete the fourth bend on the piece of aluminum — in order to keep the firearm legal.

Bishop declined to comment on the case following the verdict.

The kits were sold though Bishop’s website, www.ARFAkit.com. He only accepted cash or money order, and required that buyers did not give information about themselves.

Bishop said he is a private person and these things are not sinister.

When asked if he conducted background checks, Bishop said he had no reason to as he was just selling informational materials. When asked if he could have sold the kit to a felon, child, mentally ill person or undocumented immigrants, Bishop said it was possible.

Bishop said he did extensive research before concluding what he was doing was legal. Following the ATF raid, he stopped selling the kits he said, and did more research. He eventually again concluded he was in the right, and started selling again.

In an email to a customer shown in court, Bishop wrote “I read the gun control act quite a bit different than other people.”