A landmark class action settlement involving some of Remington's most popular firearms has officially gone into effect, after critics of the agreement declined to take their case to the Supreme Court by a Tuesday deadline, according to an attorney for the plaintiffs.

That means that millions of owners of the iconic Model 700 rifle — and a dozen Remington models with similar designs — have 18 months to file claims for a free replacement of their guns' allegedly defective triggers. The guns have been linked in lawsuits to dozens of accidental deaths and hundreds of serious injuries, though Remington still maintains they are safe.

"Anyone with one of these guns should take advantage of this opportunity to get the trigger fixed," said Eric D. Holland, a lead attorney for the plaintiffs in the class action case. "I've encouraged everyone to put these guns away. Don't use these guns. Make the claims now."

A special website has been set up with information on how to file a claim, and there is also a toll-free hotline, 1-800-876-5940.

Attorneys for Remington did not respond to an email seeking a comment.

In the past, the company has said it was settling the class action case in order to avoid protracted litigation. Earlier this year, Remington — the nation's oldest gun manufacturer — filed for Chapter 11 bankruptcy protection, citing declining sales. The company has since reorganized and emerged from bankruptcy with the settlement still intact.

The effective date of the settlement comes almost exactly eight years after CNBC first explored allegations that Remington engaged in a decades-long coverup of a defect that allows the guns to fire without the trigger being pulled.

Remington said the guns have been safe since they were first produced. But the 2010 documentary "Remington Under Fire: A CNBC Investigation" uncovered internal company documents showing engineers warning of a "theoretical unsafe condition" even before the trigger design went on the market in 1948. The company repeatedly decided against modifying the design or launching a recall, even as accidents and customer complaints continued to pile up.

The milestone also comes 18 years after the death of 9-year-old Gus Barber, killed in a hunting accident in Montana on Oct. 23, 2000. The boy's mother said her Model 700 rifle went off as she was unloading it, with her finger away from the trigger. Unbeknownst to the family, Gus had run behind a horse trailer, directly into the path of the bullet. The family eventually settled a wrongful death claim against Remington for an undisclosed amount.

Soon after Gus' death, his father, Richard Barber, made it his life's work to find answers about Remington and its products, gathering thousands of internal company documents, many of which have been published online. Barber served as a consultant to the plaintiffs in the class action case, but he resigned after concluding that the attorneys were not pressing the company hard enough.

"I'd like to believe that I have a part in getting to this time and place in history," Barber said in an interview. "I would like to believe that 15 years of my painstaking work in my detailed analysis of Remington's documents, putting the pieces of the puzzle together, made a difference in my son's memory."

Barber has been critical of the settlement, which he says is "built on a lie" — namely, Remington's continued claim that the guns are safe. But he is still urging gun owners to take advantage of the trigger replacement offer, even if it means sending their guns in for repairs just as peak fall hunting season begins.

"Why would somebody take a chance endangering the lives of their family members and friends, just because it may inconvenience them, that they may have to use a different rifle," he said.