POF MP5K + S&B NATO = Stuck and Split Cases

[Dennis]

I took my previously reliable (other than with HPs) POF MP5K to the range and the first few rounds of S&B 124g NATO failed to extract and the last one finally had to be mortared out. They were split unlike other rounds I have fired. See pics below...

I then fired a 30 rd magazine of Federal 115g ball with no issues.

Then I lubed the gun and tried the S&B again and it ran though half a mag before the same thing happened.

I stripped the gun when I got home and the chamber wasn't gunky but did have some reddish residue inside the flutes. I scrubbed it out.

I won't use any more S&B but I have run over a thousand rounds of it thru Glocks and EVO3 and Colt 9mms with no issues.

Thanks for any info!

Dennis. https://uploads.tapatalk-cdn.com/20230709/e65f5027e205b2bca6c920b8aa91909d.jpghttps://uploads.tapatalk-cdn.com/20230709/aae9f6a4780566ce80ca3a0aebb39074.jpg

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[Bret]

And to think that I was upset because my POF was denting case mouths to the point that some of them can't be reloaded. Can you try some of the Winchester NATO 124gr FMJ? I'm curious if you get the same result.