Question on neck area of chamber

[GAnderson]

I have a Factory new 224 Valk AR15 and after cleaning the barrel before firing a round, I ran a borescope in it to see what things looked like. I noticed that in the neck portion of the chamber these distinct "lines" in the neck portion...there are 4 of these equally spaced 90* apart. I chambered and fired a round and on the neck of the fired cartridge these 4 lines are visible on the neck of the brass. Any idea of what these areas represent and is this some special "design"? It doesn't effect the functioning of the rifle and the lines are very faint on the brass necks...the borescope really magnifies things. More curious of how the 4 lines can get incorporated into the chambering and what if any purpose they serve. Thanks

 

[geraldgee]

Some rifle manufacturer’s (H&K for sure) flutes the chamber to ease extraction. I am not saying that’s what you’re looking at but it sure looks similar. Google ‘chamber fluting’ for examples. Who makes your barrel?

Gerald

 

[Dusty Stevens]

Those flutes pretty much make your brass unreloadable

 

[GAnderson]

Some rifle manufacturer’s (H&K for sure) flutes the chamber to ease extraction. I am not saying that’s what you’re looking at but it sure looks similar. Google ‘chamber fluting’ for examples. Who makes your barrel?

Gerald

Thanks Gerald...while the chamber is not fluted the neck area seems to be. The "maker" of the AR is POF and when I started researching fluted chambers as you suggested, this came up from POF's web site...it is called E2 Extraction Technology...only the neck portion of the chamber is fluted and equally spaced at 90* increments. So, it appears that my question has been answered. I appreciate you at least getting me headed in the direction of searching "fluted chambers".

 

[GAnderson]

Those flutes pretty much make your brass unreloadable

Dusty, the small lines on the necks of the brass are barely visible...you really have to look hard. The entire chamber is NOT fluted just the neck portion. I see no issue whatsoever with reloading this brass...I have seen brass scratched worse that what I am seeing on the necks.

 

[Dusty Stevens]

Dusty, the small lines on the necks of the brass are barely visible...you really have to look hard. The entire chamber is NOT fluted just the neck portion. I see no issue whatsoever with reloading this brass...I have seen brass scratched worse that what I am seeing on the necks.

I guess its not like those HK chambers. You can see the flutes on that brass laying on the ground

 

[GAnderson]

I guess its not like those HK chambers. You can see the flutes on that brass laying on the ground

You are correct...it is not the entire body of the brass at all...just the neck. The borescope really makes it look extremely more pronounced than what it actually is. Thanks

Gene

 

[338 dude]

I have a Factory new 224 Valk AR15 and after cleaning the barrel before firing a round, I ran a borescope in it to see what things looked like. I noticed that in the neck portion of the chamber these distinct "lines" in the neck portion...there are 4 of these equally spaced 90* apart. I chambered and fired a round and on the neck of the fired cartridge these 4 lines are visible on the neck of the brass. Any idea of what these areas represent and is this some special "design"? It doesn't effect the functioning of the rifle and the lines are very faint on the brass necks...the borescope really magnifies things. More curious of how the 4 lines can get incorporated into the chambering and what if any purpose they serve. Thanks

POF patriot ordinance factory also used to do that to help with extraction

 

[GAnderson]

POF patriot ordinance factory also used to do that to help with extraction

This is a POF rifle...

 

[Gappmast]

The neck on that cartridge sure is dirty

 

[GAnderson]

The neck on that cartridge sure is dirty

No it isn't...I edited the pic so that the lines would show better. It is a nickel casing and the neck is shiny as a baby's butt. Just the way it looks in the pic.

 

[Rustytigwire]

Very informative, great post everyone.

 

[spclark]

How does some chamber neck ‘treatment’ that’s supposed to aid case extraction affect gas-sealing at the neck?

I’d have to believe anything other than a smooth, consistent neck ID surface would lead to gas leaking back onto the case shoulder & side wall?

Or maybe that’s the secret? Let a little gas pressure escape backwards so case is ‘blown free’ of the chamber before extraction?

 

[338 dude]

How does some chamber neck ‘treatment’ that’s supposed to aid case extraction affect gas-sealing at the neck?

I’d have to believe anything other than a smooth, consistent neck ID surface would lead to gas leaking back onto the case shoulder & side wall?

Or maybe that’s the secret? Let a little gas pressure escape backwards so case is ‘blown free’ of the chamber before extraction?

Exactly

 

[Bc'z]

So is this a DI operating system or the piston.
I'm gonna have to look at some fired brass.
I've got a POF15 piston gun that runs super clean and I've never noticed this.

 

[geraldgee]

GA

couple questions if you dint mind-
Piston driven?
How is accuracy?
It’s a nice rifle. Good luck with it

Gerald

 

[GAnderson]

So is this a DI operating system or the piston.
I'm gonna have to look at some fired brass.
I've got a POF15 piston gun that runs super clean and I've never noticed this.

It's a DI system and the brass comes out really nice and clean. The reality surrounding the fluted neck may be all "smoke and mirrors"...who knows. I just kind of was taken aback when I saw this with the borescope and then looked real close on the brass and saw the "matching" indications on the necks of the brass.
I wonder if they use some EDM method to put the "v" grooves in the chamber neck? Hard to imagine how else it could be done.

 

[GAnderson]

GA

couple questions if you dint mind-
Piston driven?
How is accuracy?
It’s a nice rifle. Good luck with it

Gerald

It is direct impingement Gerald. As for accuracy, I haven't got that far...was getting the scope zeroed and then it started raining. Only got to fire 3 shots before the rain came.

 

[GAnderson]

How does some chamber neck ‘treatment’ that’s supposed to aid case extraction affect gas-sealing at the neck?

I’d have to believe anything other than a smooth, consistent neck ID surface would lead to gas leaking back onto the case shoulder & side wall?

Or maybe that’s the secret? Let a little gas pressure escape backwards so case is ‘blown free’ of the chamber before extraction?

Here is what the brass looks like straight out of the chamber...really very clean. This is a brand new rifle and these are the first 3 rounds fired thru the rifle, so after several more rounds the brass will probably be a little more "sooty" as things get dirtier.

 

[Bc'z]

So I checked out some of the brass I shot a couple weeks ago.
No lines like the ones you have.
But I did notice a coupe of scratches that are consistent on the shoulder body junction and front half / edge of neck only on this one side, and on all brass fired.
Looks like its dragging on something on the way in or out of the chamber.