I’ve been trying to pin down the relationship between these two US companies, both of which have been involved in the design of ammunition (mainly for auto cannon), particularly in the 1960s and 1970s. Their names appear together in the Amron Aerojet .330 multiple flechette round, and there also seems to have been cooperation between them on other occasions. For example, when researching the 27.5 mm Bushmaster project, I find some sources say the ammo was made by Aerojet, some say Amron, some say both… As far as I can tell, they remained separate companies.
Briefly from H.W.S. Vol. 3, pp 426-428:
Aerojet started work on the .330 Multiple Flechette Cartridge in 1968. AMRON and Aerojet had worked together on the 30x173mm cartridge case. Aerojet subcontracted AMRON to improve the .330 cartridge case which resulted in the 8.38x69mm cartridge case, initially made of brass, but by late 1970 AMRON was supplying Aerojet with aluminum cased rounds.
Quoting BOCN Forum member “weberoed”-
“Aerojet spun off their proj business, Ford Areo Space picked it up, then Honeywell took that over, finally it all went to Olin Corp, then Olin Corp sold their defense business to be come Primex which is not General Dynamics -Ordnance and Tactical Systems in Marion, IL (I worked for Primex and GD-OTS). The 30mm buisness was taken away from Primex and it all went to ATK. In a display case at Marion the 27.5 mm rounds you pictured were on dispaly with a number of other experimental rounds from Aerojet and Ford Aerospace.”
IAA Forum discussion on Aerojet 27.5 x 160mm ammunition:
Not the full answer to the initial question but I spoke to a person who visited AMRON in the late 1970s and early 1980s. The guy is well into medium calibers and well informed so I got his permit to cite his answer to me. Here what he said:
Back in that time the plant in Waukesha was making only brass and steel cases + all sort of components. Cases including 30x173 GAU-8/A were delivered to Aerojet. At AMRON Waukesha only TP loads for internal case QA were loaded and fired. Before AMRON had decided to go big in medium calibers they also made (commercial) 9x19 and .45 ACP cases but later ceased production (used Manurhin Machinery).
As said this here is only a limited peer through the keyhole and is a part of the mosaic.