PCP Ammunition, out of Orlando, FL, has debuted an interesting line of polymer-cased precision rifle ammunition at the 2012 Media Range Day. The PCP cases are of two-piece polymer construction, and use projectiles from Sierra and Berger Bullets.
PCP Ammunition claims that their ammo is being more accurate than conventional brass-cased ammo, while being up to 33% lighter. In addition, the polymer cartridge acts as an insulator, reducing the ammount of heat conducted to the barrel. Casual testing with their demo guns seems to bear this claim out – a fired .300WM PCP case was not even slightly warm upon ejection from the demo rifle.
PCP Ammunition is currently available in .308 Winchester and .300 Winchester Magnum, and .223 Remington rounds are in development.