Complex sentence: The AEK-971 is based on previous AK rifles in internal design and layout, but is also equipped with a recoil-balancing mechanism by way of a counter-weight that negates the impulse of the gas piston and bolt carrier, resulting in more controllable automatic fire.
Split into simpler sentences: The AEK-971 is based on previous AK rifles in internal design and layout, but is also equipped with a recoil balancing mechanism. The rifle has a counter weight that negates the impulse of the gas piston and bolt carrier: this is the balancing mechanism and results in more controllable automatic fire.