I examined the picture of the W.R.A. 43 9 mm round against a W.R.A. 43 round of .30 Carbine caliber. I think that the bunter that marked that 9 mm cartridge was a standard .30 Carbine bunter.
In checking the one round I retained as a box specimen in my box like Lew’s, I find the box is dated from 1942. In my mind, that would tend to eliminate the possibility of the W.R.A. 43-dated round being a prototype for that series of 9 mm ammunition in WWII, since one year earlier they were already making serial production of the W.R.A. 9 M-M headstamped cartridges.
That would leave a couple of possibilities (maybe more). Firstly, that the headstamp is simply an error. That is, a .30 carbine bunter was accidentally left in the loading machinery. Such mis-headstamps are widely known I have a few examples in my own collection. Does that negate its interest? Heck no. The headstamp is the headstamp. As me if my .30 Luger with “LUGAR” misspelled with a letter “A” instead of “E,” is a prized round in my collection!
The only way to prove or disprove the above would be if research could determine whether or not .30 Carbine and 9 MM Luger were loaded on the same line and basic machinery, off and on, at Winchester in 1943.
The second possibility is that it was done purposefully to mark a small lot of ammunition for some specific test, perhaps with an eye to product improvement. I don’t know how, at this stage, this could be proved unless test results were found that included mention of the headstamp used on the ammunition involved.
Regardless, it is a great find either way, or if made for some other reason that simply doesn’t come to mind right now. Wish I had a hundred or so boxes of that ammo to go thru myself!