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· Platinum Bullet Member
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The Japanese Type 99 gas adjustment operates by throttling the gas entering the gas cylinder from the barrel port, not by metering the exhaust. There is a scribe mark on the left side of the gas block, at about 11 o'clock, with which the gas adjustment spindle is indexed. The spindle has five numbered and detented orifices of different diameters that can be rotated into alignment with the larger barrel port. The smallest orifice (the least amount of gas) is Number 1, and the largest is Number 5. Since the spindle is threaded and bottoms out at Number 1, opening it to a higher setting slightly increases the volume of the gap in front of the piston head, which also tends to boost the available energy.

There can be little doubt that the T99 does employ primary extraction. The front wall of the locking recess in the bolt is not vertical, but is cut on an angle that is easily seen in profile. This allows the bolt to move backward slightly as the locking block is withdrawn, before unlocking is completed.

This design was very well thought out, and the gun was admirably suited to the combat conditions in which it served. It is rugged, accurate, well closed-in against the elements, reliable and easy to disassemble and maintain, superior in many respects to the BAR. A U.S. Army veteran of New Guinea and the Philippines related to me that his unit made it SOP to reinforce their own line with every T99 and T96 they could capture; the only limitation being sufficient ammunition.

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