"You should play a constructive role in our national dialogue by refraining from broadcasting the NRA 500," Murphy writes. "By airing this race you will be strengthening the brand of a radical organization that is currently standing in the way of meaningful progress on this issue."

The April 13 event at the Texas Motor Speedway is the first time the NRA has sponsored a NASCAR Sprint Cup event.

According to Murphy and media accounts, race winners will be awarded firearms while posing for celebratory photographs after the event. 

"The race not only brings national attention to an organization that has been the face of one side of this heated debate, it also features the live shooting of guns at the end of the race," Murphy said.