Intermediate-length 7075-T6 receiver extension for BCM MK2 buffers and an M16 rifle action spring.

The BCM MK2 Receiver Extension uses intermediate-length internal geometry. BCM requires a matching MK2 buffer and an M16 rifle action spring, so carbine and full-size rifle buffers are not substitutes.
Add the BCM MK2 Receiver Extension to your build and see how it enhances your platform.