[11][12] In order to determine the suitability of the rifle, it was issued in limited numbers to the Japan Self-Defense Forces for field testing purposes.

After the data collected from the field testing stage of the AR-18 was examined, formal development of the next-generation assault rifle began with its designation as the HR-16 (HR1604).

Also, due to the use of aluminum and thermoset plastic as opposed to the steel and wood construction of the Type 64 rifle, the speed with which a soldier could react to a threat was increased.

This is further complicated because the procurement method for the weapon is limited to single fiscal year accounting and further reductions in manufacturing process costs are currently non existent.

[17] However, the magazine produced specifically for the Type-89 uses a follower that has a special shape to hold the bolt open after the final round is spent.

However, this comes with the hidden cost of allowing sand and other foreign bodies to enter the magazine easily and cause malfunctions in the operation of the weapon.

Since the ammunition developed for the Type 89 rifle is produced in Japan, it is head stamped with the sakura mark of the Self Defense Forces instead of the typical NATO circle-cross used on the SS109/M855 round.

Also, the Type 89's handguard is molded with inlets along its lower edges in order to accommodate the legs of the bipod if they are folded inwards for storage.

In 2004, JSDF elements that had the possibility of seeing combat were issued an optic (an unmagnified red dot sight) with their Type 89 along with a mounting bracket in order to decrease target acquisition time.

[17] However, since the use of the sight is still in its provisional stage, individual JSDF members are expected to purchase their own commercially available model for use in a possible combat theater.

[24][25] During the initial deployment in Iraq, JSDF elements that had the possibility of seeing combat (for example the Western Army Infantry Regiment) were issued a removable foregrip[8] and a 25 mm Weaver rail was installed under the front handguards of their Type 89s to accommodate it.

Shortly afterwards, the restriction was lifted and all units began to receive foregrips despite common complaints about damage to the handguards that were caused by the mount.

[8] A three-point sling was issued to JSDF elements that had the possibility of seeing combat due to the positive testimonials of various international military and police forces.

[27] Publicity photographs taken at exhibitions hosted by the Technical Research and Development Institute of the Japanese Ministry of Defense (TRDI) also show that the third generation of the prototyping process for ACIES has now produced a full size version of this modified Type 89 with a retractable stock and rail system.