Designed by Sharps Rifle Company for use in AR-platform rifles, the .25-45 Sharps cartridge reportedly fires an 87-grain, .25-caliber Speer Hot-Cor bullet at a muzzle velocity of 3000 fps. The new cartridge is based on the .223 Rem., which means the only thing you need to convert your AR-15 to .25-45 Sharps is a new barrel.
Dave Campbell recently wrote a good report on the cartridge. Here's an update with info just obtained at the 143rd NRA Annual Meetings & Exhibits.
Tim Lesser, the company's vice president of sales and marketing, says AR barrels chambered in .25-45 Sharps will be available in June 2014. Black Forge and Black Rain Ordnance will produce complete upper receivers shortly thereafter. The 87-grain Speer Hot-Cor load will be in stock at Brownells, Midsouth Shooters Supply and Natchez Shooters Supplies in June as well.
