(CNN) — A record number of people are dying from firearm injuries in the US, and new research suggests that shootings are becoming more lethal, too.

Most victims of fatal firearm injuries die at the scene of the shooting, before they can be treated in a health care setting. But that has become increasingly common over the past two decades.

About 57% of firearm fatalities in 2021 occurred at the scene of the shooting, up 9% since 1999, according to a research letter published Wednesday in the JAMA Surgery journal. For this analysis, researchers used data from the US Centers for Disease Control and Prevention and excluded suicides and other self-inflicted firearm injuries.

Nearly 49,000 people died from firearm injuries in the US in 2021, CDC data shows — an unprecedented surge of about 23% over two years during the Covid-19 pandemic.

And a shift in the type of firearms that are being bought and used is a key factor making shootings more lethal, experts say.

“It’s leaning more and more towards military-grade, higher velocity, higher lethality type of weapons,” said Dr. Eric Fleegler, an emergency physician at Boston Children’s Hospital.

“That includes larger magazine capacity so they can shoot more bullets, the ability to fire them at faster rates, and quite frankly, just bigger, faster bullets which cause more damage to a human body.”

Federal data shows that handguns are the most common murder weapon, used in more than half of all homicides that involve firearms. But rifles, such as the AR-15, are becoming more frequently used.

Nearly 4% of firearm homicides in 2021 involved a rifle, killing 447 people, according to data from the Federal Bureau of Investigation. That’s more than twice as many deaths and nearly twice as common compared to firearm homicides in 2015.

Other external factors could also play a role in the location where a victim dies, such as increasing demand for ambulances that could affect emergency transportation options.

Still, experts say that more — and better — data on gun violence is needed.

In the CDC data, for example, definitions to help differentiate location of death were lacking and many were coded as “other” or “unknown.”

And the true scope of America’s gun epidemic is far broader than the deaths it causes, experts say.

“Deaths from firearm injuries are horrible tragedies, but they are unfortunately just the tip of the iceberg,” said Fleegler, who has studied gun violence but was not involved in this research.

There are many others who suffer physically from gunshot wounds and a deep emotional toll on families and communities, he said, and more robust data is needed to understand that.

While there are more questions to be answered, experts say that this new research adds to evidence that an important step to reducing gun violence will involve addressing the types of guns that are available.

“It reiterates that maybe there should be a look at solutions which limit the magazine capacity and access to high-caliber weapons, as well,” said Ari Davis, a policy advisor at the Johns Hopkins Bloomberg School of Public Health Center for Gun Violence Solutions.

Gun violence in the US has become more lethal, research suggests