Don't believe I've seen this before...

[josh2600]

Any ideas? Not from my gun, just range pickups at harvard, wondering what caused this... They're 9mm cases, both Blazer.

 

[MSant]

Looks like reloads without case lube

 

[Customrust]

AET chamber from schuemann barrel

 

[soam]

H&K MP5s also leave those marks as they have a fluted chamber.

 

[Another_David]

H&K MP5s also leave those marks as they have a fluted chamber.

yup

 

[eisenhow]

Yup HK. I came across some 40 cases like that.

 

[josh2600]

Ah, it was in a class 3 okay area, so that's likely it. thanks guys.

 

[NavelOfficer]

You'll see this on many .308s that are fired in H&Ks and PTR's (I think these are the culprits) with the fluted chambers.Some really forge heavy grooves into the brass.

 

[soam]

Ah, it was in a class 3 okay area, so that's likely it. thanks guys.

If they were on the subgun range (the one with the steel) I may very well have fired some of those

 

[PixelPusher]

H&K P7s also have fluted chambers and leave that same mark on the brass.

 

[cockpitbob]

Why would they flute the chamber? Give dirt and grit a place to go?

 

[EddieCoyle]

It helps with extraction.

Some firearm designs use non-rotating bolts that lack the power of a cam to initiate extraction. Without fluting, these guns would rip the rims off the cases.