UTM has a stripped down kit, called the Core Kit, which is just the bolt carrier group, magazine and 50 rounds of ammo for $294.  Basically it just doesn’t have the targets, traps and cleaning kit.

UTM RBT Target Conversions are designed for utmost safety, in-service reliability and maintainability. The UTM RBT AR-15 Bolt Carrier Group Conversion is expertly engineered with Fail-Safe measures to prevent the discharge of a standard ‘“live”’ round. UTM RBT Conversions are easy to install, just a simple exchange of the manufacturer’s Bolt/Carrier Assembly.

Details:

• Plastic projectile weighs less than 1 gram
• Average velocity of 375 fps at the muzzle
• Outstanding Short Range Accuracy, .223/5.56mm ammunition = 1.18” group at 32 yards
• Noise level at 113db – hearing protection recommended
• No Gunpowder – primer actuated systems
• UNIQUE patented, proprietary and exclusive dual primer system and projectile driving band system.
• The UTM RBT Civilian Target Ammunition (CTA) Conversion WILL NOT fire standard .223/5.56mm live rounds because of its offset firing pin design
  Cartridge technology has over a 99% reliability as certified by the U.S. Army’s Picatinny Arsenal