Identification request- found these cartridges while scuba diving at old fort

I found these “cartridges” while scuba diving off of Fort H.G. Wright- Fishers Island - New York. Does anyone recognize these things or can they identify them? Rifle cartridge?

Fort H. G. Wright was built as part of the large-scale Endicott Program, which replaced US coastal defenses. The fort was designed and built by the Army Corps of Engineers, the weapons were designed by the Army Ordnance Corps, and the forts were (by 1907) garrisoned by the Coast Artillery Corps. The fort was active in WWI and WWII, deactivated in 1947, and abandoned in 1948 with all guns scrapped. In 1949 the Naval Underwater Sound Laboratory established a facility on the island.


The two items you show in your photo are primers used to fire large caliber guns such as used by the Coast Artillery Corps.

Here is an article from The Coast Defense Study Group Journal on primers & firing mechanisms plus some relevant diagrams contained in the article-

Artillery Friction, Obturating & Standard Primers.pdf (1.6 MB)



Wow that was fast! Thanks! I never would have figured that one out myself… Thanks for the detailed response!!!


Thanks a million to Brian!!!

The next step for me is to find out what primers they are and how old. I can only post one photo at a time. Here is the first

The markings read “ASMPU 218” as best I can tell. Any thoughts on how to get an ID?


Hopefully someone else will jump in and help, I don’t have any info identifying makers of these types of primer.