By Peg Brickley and Andrew Scurria

Remington Outdoor Co.'s second chapter 11 filing since the 2012 Sandy Hook school shooting puts a long-running lawsuit by victims' families at risk, threatening to bury details of how the company's popular assault rifles were marketed.

After the gun manufacturer sought chapter 11 protection on Monday, the families of nine Sandy Hook victims said the bankruptcy filing shouldn't shield Remington from having to answer allegations about its marketing of the Bushmaster XM15-E2S rifle, the weapon used to murder 20 first-graders and six adults.

Last year, Remington tried and failed to get the U.S. Supreme Court to quash the lawsuit, which accused the company of improperly marketing the weapon to civilians for use in military-style combat against perceived enemies. When the nation's highest court declined to hear Remington's appeal in November, it cleared a path for legal discovery to be taken from Remington.

Now, lawyers for the families fear this bankruptcy, unlike a prior chapter 11 restructuring of the Huntsville, Ala., company, will enable Remington to avoid handing over the internal documents they hope will support allegations that unscrupulous advertising inspired Adam Lanza, the shooter at Sandy Hook.

"We cannot begin to prevent future tragedies until gun manufacturers face consequences for wrongful conduct that prioritizes their profits over public safety," said Josh Koskoff, a lawyer for the families.

They are calling on big Remington shareholders JPMorgan Chase & Co. and Franklin Resources Inc. to allow the claims to progress despite Remington's chapter 11 filing and its automatic halt on litigation.

If Remington doesn't agree to relinquish its bankruptcy protections, the judge presiding over the bankruptcy would need to grant special authorization for discovery to proceed in another forum.

Remington declined to comment on the Connecticut case. JPMorgan also declined to comment. Franklin couldn't immediately be reached for comment.

Remington also filed for bankruptcy in 2018, cutting roughly $775 million in debt and wiping out its previous owner, Cerberus Capital Management LP, while leaving the Sandy Hook litigation unaffected. Despite the restructuring, Remington was still stuck with loans that tied up much of its cash.

The gun industry's fortunes tend to rise and fall based on the country's political climate. Under former President Obama, firearm sales grew as enthusiasts worried about potential regulation, while sales softened after President Trump took office pledging to defend gun rights.

Demand has skyrocketed again since March as measured by Federal Bureau of Investigation background checks, driven by Americans' concerns about personal safety during the coronavirus pandemic and, more recently, the civil unrest following the police killing of George Floyd.

But even as gun sales surged nationwide, Remington didn't have the inventory to meet rising demand or the cash to buy raw materials and step up production, according to court papers.

The company had been searching for potential buyers and was in talks to sell itself out of bankruptcy to the Navajo Nation before negotiations collapsed in recent weeks, forcing a chapter 11 filing without a clear bidder in place.

Most of Remington's cash is tied up by lenders, meaning the company can't simply reshuffle its balance sheet to get out of bankruptcy.

"The exit strategy is a sale," said Stephen Warren, one of Remington's restructuring lawyers, at the company's initial appearance in bankruptcy court on Tuesday. At least four potential bidders are inspecting the business, he said during a hearing in the U.S. Bankruptcy Court in Decatur, Ala.

Although the Navajo Nation could yet be a potential contender to save the historic business, Remington is inviting bids for all, or parts, of its business.

Lenders aren't giving the company much time, according to court papers. It wants bids by Sept. 1 and is willing to sell its firearms and ammunition businesses separately to pay down $254 million in secured debt, including a $12.5 million loan from the city of Huntsville, Ala.

Law firm O'Melveny & Myers LLP and investment bank Ducera Partners LLC are advising the company. The case number is 20-81688.

Write to Peg Brickley at peg.brickley@wsj.com and Andrew Scurria at Andrew.Scurria@wsj.com