"when used with the ammo it was designed for" This got me curious.
Well, it's way above my pay grade to figure out. The C.I.P ( international standards) had the cartridge listed long before the US military got dimensions & samples from Finland & submitted it to SAAMI in 1979. When SAAMI was through their test didn't agree completely with CIP.
Then,,,, a few years later Ruger wanted to chamber it in a platform that was basically designed for, the 223. But, they had to change some chamber dimensions to lower pressures that would better suit the Mini & submitted new dimensions to SAAMI.
Now, I'll admit after looking back and forth between CIP, SAAMI 1, SAAMI 2 for Ruger, & what has been made since 40's but one maker decided to change for their own use, I just threw in the towel & stopped reading.
Any Philadelphia lawyers here?
Further reading here seem s to indicate the firing pin is the big issue & the ins & outs of that has been explained very well by Hylander. But I never got that far with the research I was doing due the feed failures.
I didn't set out to start controversy here, but it seems everywhere I looked there was controversy about both the cartridge & the rifle itself. Maybe I was looking for love in all the wrong places.