Colt Defense has filed for bankruptcy protection, as it grapples with a heavy debt load.

The Connecticut-based gunmaker says it plans to continue its normal business operations during its restructuring.

The company is struggling with more than $350 million in debt, as well as waning sales.

Colt’s fortunes were hurt by the loss of a contract in 2013 to supply the US army with its M4 assault rifle.

Keith Maib, the company’s chief restructuring officer, said: “Colt remains open for business and our team will continue to be sharply focused on delivering for our customers and being a good commercial partner to our vendors and suppliers.”

Colt has been plagued by financial problems in recent months.

In November 2014, Colt took out a $70 million loan from Morgan Stanley to help make an interest payment.

But in May 2015 it missed a $10 million interest payment.

Last year sales of Colt’s sports rifles and handguns fell 30%.

The company has a long US history, known for making American firearms for more than 150 years.

Colt previously filed for bankruptcy protection in 1992, emerging again two years later.