From NRA’s First Freedom:

When dedicating the Gettysburg National Cemetery in 1863, President Abraham Lincoln honored those who gave their “last full measure of devotion” to defending American freedom. A few years later, Americans began to commemorate “Decoration Day” on May 30 as a time to visit the graves of those who had given their lives during the Civil War. Later, Decoration Day became Memorial Day, honoring the sacrifices of all American soldiers.
Just a few years later another institution was created that is closely related to Memorial Day: the National Rifle Association.
Founded in 1871, the NRA began by dedicating itself to the safety of American soldiers. Because of the efforts of the NRA over the ensuing century and a half, many more American soldiers have been able to accomplish their missions and to return home alive.