Addition from Daniel Watters:
“History of Modern U.S. Military Small Arms Ammunition, Vol III” mentions that there were different cases used by Lake City AAP. Some were formed from a 7.62mm NATO cup, while others had a purpose-made cup that ended up with with a 2 gr. larger internal capacity. While 26 gr. of WC860 was used for early testing, Frankford Arsenal switched off to a slightly lighter charge of 24.3-24.5 gr. of WC860 for the reference lots. Another interesting point was that the WC860 from Badger AAP gave higher velocities than that from Olin’s East Alton plant. (Badger AAP was a GOCO facility run by Olin.) HPC2406 was tested, but dropped for excessive flash.
Roughly ten years ago, I stumbled across a site hosting the annual command histories for the Commander in Chief Pacific (CINCPAC) from 1960 through the mid-’80s. I found an interesting tidbit in the 1970 history regarding US production of 7.62x39mm ammunition for the Cambodian Army.
Commander in Chief Pacific Command History 1970 – Volume II, pp 259-260
Assistance for the Cambodian Army
(TS) The U.S. and RVN began supplying FANK with captured AK-47 rifles and ammunition in April; however, an additional source was needed to meet FANK requirements. (Redacted text) The remaining 1,420 AK-47 rifles were scheduled for delivery on 17 January 1971.2
(TS) On 31 December, Cambodia MAP was supporting a density of 68,973 weapons that fire AK-47 ammunition. After delivery of the remaining Indonesian AK-47s, the density will be 70,393 weapons. The 30-day ammunition consumption rate will be 8.73 million rounds. To provide a guaranteed continuing source of supply to meet the Cambodian MAP requirement for AK-47 ammunition, production is underway in the Continental United States (CONUS) under a contract paid out of Cambodia MAP funds. CONUS production was 20 million rounds for the period October through December. On 8 January 1971, the SECDEF approved CINCPAC’s request to increase CONUS production to 9.5 million rounds per month. The first two million rounds of CONUS production AK-47 ammunition was airlifted to the RVN on 20 November. The first surface delivery arrived on 1 December with 5.96 million rounds delivered by 31 December. An additional 9.180 million rounds was scheduled to arrive by 13 February 1971.1
(Redacted text) He stated that costs being equal, insertion of M-16s into Cambodia as the standard infantry weapon was much preferred to building a weapon system (AK-47) which was not U.S. supportable without parts engineering or tenuous third country support. However, additional AK-47 could be utilized provided they were procured at no cost to MAP and with no strings attached.2
2. J4312 Point Paper, HQ CINCPAC, 28 Oct 70 and 8 Jan 1971, Subj: AK-47 Rifles/Ammo for Cambodian MAP.