The man, known as David, said he wanted answers about how Lincolnshire Police dealt with allegations against Gordon Dawson, a farmer from Spilsby.
Mr Dawson shot himself in 2007 after officers informed him of the inquiry.
In a statement, Lincolnshire Police said "procedures were correctly followed at the time" but policy has subsequently changed.
David claimed Mr Dawson had repeatedly abused him from the age of 15.
According to Lincolnshire Police, the first allegation was made in 1999 but no action was taken due to "insufficient evidence".
In 2006 police arrested Mr Dawson after four other men came forward claiming they were also abused as children between 1964 and 1986.
In early 2007 another alleged victim came forward.
An investigating officer phoned Mr Dawson on 23 March 2007 to tell him he would be questioned further and a few hours later he was found dead at his home.
Following Mr Dawson's death the investigation was dropped but David later complained to the police about the way the investigation was handled.
Speaking on the BBC's Victoria Derbyshire programme, David said: "We've had no justice, no finals, no process.
"It's been shutdown, shutdown all the way. I just want some answers."
Supt Rick Hatton said: "We have revisited the circumstances surrounding the investigation into Mr Dawson and are satisfied that the investigation that took place was thorough and robust, and no misconduct took place.
"However, a number of lessons were learned in relation to best practice and fed back to the Public Protection Unit.
"We are very sympathetic to the position of the victims in this case and appreciate they may feel that Mr Dawson was not brought to justice."
The force said any similar situation today "would see Mr Dawson's guns removed from him as policy is now quite different".

They read from Attack of the Shidas about children from different Kenyan communities working together to protect their well from an alien invasion.
The event is meant to foster a culture of reading in the country, the organisers told the BBC.
The US currently holds the Guinness World Record set by 233,000 people.
It will take at least a week to work out whether they have been successful as they need to tally the number of pupils from across the country who participated.
Kenyan children's book author Muthoni Muchemi led the event with 1,700 students reading from her book at Hospital Hill Primary School in the capital, Nairobi.
Afterwards, she said she wanted to break the stereotype that Africans do not care for books.
"Growing up I would always hear that if you want to hide something from an African, put it in a book - and it was really upsetting to me," she told the BBC.
"I want to help change that perception and the first step is to re-introduce reading not just as important but enjoyable," she said.
"I have seen over the years that a lot of families don't have libraries in their homes but have they have big TVs. We need to get parents to understand that reading for pleasure with their children is an important part of brain development."
The 13- and 14-year-olds, dressed in grey and white uniforms, who chorused the words at Hospital Hill Primary School said they enjoyed the challenge.
"I enjoy reading because it teaches me about other people and places. It teaches me about the world," one girl said.
Another student said he thought Attack of the Shidas had important life lessons about working together and accepting people's differences.
It is not the first time Kenya has tried to break the record - last year 142,279 children read aloud in 360 schools.
This time, Ms Muchemi is more optimistic about the Storymoja National Read Aloud attempt.
But she says in the end it is about building confidence in children.
"If you master reading it means you've increased your vocabulary, you have good command of sentence structure, your facility with language is improved. It can't help but build your confidence," she said.
"Exposure to different stories makes you more confident in your place in the world because you no longer feel alone. It's served me very well because I grew up in a deep rural area."
Police have denied mishandling a sexual abuse investigation which left a victim claiming he had been denied justice.
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Pupils at about 400 Kenyan schools are trying to break the world record for having the most people reading aloud simultaneously from the same book.