Strange brass -- Flutes on neck

[bob88robert]

I just got into reloading and ordered some range brass. I got 2 casings that looked like this. Any idea what would cause this? It's a .308 win.

 

[okie]

VV

 

[Charliemac]

It was fired in gun with a fluked chamber. I had a HK91 that did that. I think it has related to how the action functions.

 

[okie]

I have one chamber like that---the brass has lasted longer than expected

 

[okie]

It was fired in gun with a fluked chamber. I had a HK91 that did that. I think it has related to how the action functions.

fluted?--I think you are correct

 

[Clancy]

Fluted chamber. A handful of foreign semi jobs are designed this way.

 

[Rick in Oregon]

There are many full auto military MG's and similar that employ fluted chambers to facilitate easy ejection when there is no issues with the brass being striated as shown.

 

[Adam in WI]

Delayed blowback semi auto

 

[Rick300]

Yep. I used to have an HK91 and it did that.

 

[joshb]

Yup! Fluted chamber. What I want to see is a pic of the reamer that cuts it! How’d day do dat??

 

[okie]

Yup! Fluted chamber. What I want to see is a pic of the reamer that cuts it! How’d day do dat??

I bet its hammered on mandrel

 

[M-61]

From Sleepy gator:
“HK roller-locked weapons use a development of Edward Stecke's patent. The bolt head, while bore pressure is still high, exerts pressure against both the firing pin carrier and the barrel extension locking abutments. The bias is toward the firing pin carrier, which is forced to the rear, along with the bolt carrier, and allows the rollers to move inward and the bolt to unlock from the barrel extension. All this occurs with high residual bore pressure. This would normally cause severe extraction problems because of the case being forced against the chamber walls. The flutes, very shallow grooves arrayed around the chamber and whose depth tapers to nothing toward the chamber rear, allow propellant gas to "float" the case free of the chamber walls and to be extracted. Examine case rims for extractor marks and you will see that they still do not come too willingly. The action is violent and very fast, often throwing cases thirty feet or more. But, it also continues to function when dirt is in the action. It is an excellent system; simple, reliable and robust.”

Also Cetme

 

[CJ6]

HK chambered.

 

[Krogen]

I have a PTR-91 (HK-91 clone) that does that to brass. At noted by M-61 above, the cases come out hard and fast. I swear, it flings them into low earth orbit. I think the rifle is more dangerous on the starboard side than downrange. It is decidedly not a target rifle, so I don't bother to load for it. Besides, I loose a lot of cases and those I do find are rather "ugly."

 

[divingin]

Had a friend shooting his HK P7 pistol the other day. Was surprised that it had a fluted chamber as well. I always liked the pistol, but didn't remember seeing what it did to brass before.

 

[chop house]

Delayed blowback semi auto

winner. ala HK-91.

 

[NV_Dmax]

It does it in the G3 as well

 

[shoobe01]

The 91 is just a civilian legal (per German and US law) G3. No difference for barrel, chamber, delay action etc.

For .308, fluted chambers are far and away most likely to be encountered on these guns.

Flute marks have no apparent impact on brass life, are purely cosmetic.

 

[jpjulian]

Don't believe anyone saying brass from a fluted chamber is ruined. It will reload just fine. Full length size and trim as you would any other case and load away. I used many, many in my M1A a number of years ago.

 

[DiffEQ]

Yah, my P7s used to throw the brass more than 20'.