Is there a difference between the 5.7 Johnson and .22 MMJ cartridges?
As a side note a friend is jonesing to rechamber a carbine to .300 Blackout (7.62x35) and deep seat in a similar manner to your .30 Kurtz.
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I believe they are the same cartridge by Johnson, there was a 22 carbine wildcat too. Johnson really attempted to interest the military in the 5,7mm, advertised 3000 fps with a 40gr bullet but
the 222 Rem Special was just about to surface and the rifles.
Lake City 7,62 NATO blanks work really well being formed into 7,92x33, some even leave the primers if unfiredAttachment 132950