40mm grenade launcher on the AP-2H Neptune

[thatguy96]

I've spent a lot of time reading up on various odd-balled COIN aircraft and the AP-2H Neptune is of a certain interest to me because of the notes in most sources about a 40mm grenade launcher. It is said that the later aircraft of the relatively small number converted were fitted with a 40mm automatic grenade launcher in the bomb bay area of the aircraft. One source lists it as the XM149. The only reference to the XM149 is for an armament subsystem for the OH-58D Kiowa Warrior (which I'm now interested in as well).

I'm wondering if this was in fact the M129 was used on the AP-2H or what, and if anybody has any additional information on the weapon used or how it was actually fitted.

Source for the XM149 Armament Subsystem is:

https://aais.ria.army.mil/aais/MISC/syscodes.pdf

[thatguy96]

Well, seeing as I've also asked this question elsewhere, I'll post the updates.

Here is a picture of part of the system, which comprised a total of 8 "XM149" launchers.
http://www.vah21.org/40mm.JPG

Now, the two prevailing theories at this point are that the XM149 was a variant of the M129 specifically for this mount, or that the XM149 was in fact the designation for the complete system, not any individual weapon. Both are interesting in the fact that this was a US Navy aircraft, so this means the weapon or the system had to have been developed by the US Army for some use prior to its installation on the AP-2H.

[Crewdog]

Is this the same system that was used on thnose of some Uh-1's during the Veitnam war? If so it was also used on some CH-47 gunships as well. Looks like it would fit in that little nose turret. I do believe a model of the Cobra was also fitted with a nade launcher in the chin turret it had.

As for how it was fitted in the bomb bay of the Neptune one could only guess. With eight of them I would have to guess that is was a special pod built and inserted for mission specific loadouts. Though if it is forward firing or rear firing I would not know.

[thatguy96]

The M5 subsystem that was fitted to the ACH-47A and the various armed iterations of the UH-1 series (B/C/M) featured the M75 40mm grenade launcher. The M129 was an upgraded version of the M75, and this was featured in the M28 series of turrets for the AH-1 series (their use on the G model being most notable).

These weapons are either related to the M75/M129, or are either M75 or M129s and the subsystem is what was known as the XM149.

The mount was originally designed to have the weapons simply shoot straight down, and they were later angled independantly to apparently allow for a football size area to be saturated by a 3-second burst at about 1,250 ft.

[Apogee]

interesting info. thanks guys