I am doing some research on Helmet test cartridges and looking for sources and information.
I know the Germans produced P08 helmet test cartridges in 1944 and the US produced them throughout WWII (HWS Vol II pg17). A scan of current ballistic testing of helmets seems to imply that specialized cartridges are no longer used. I also have a post-WWII German helmet test cartridge.
I can find no evidence that either the US or Germany produced and used helmet test cartridges before WWII. Did other countries use helmet test cartridges and if so when and in what calibers?
Any information will be a help.