Black powder marks around case head groove .223

[timelinex]

I made a load for my Daniel defense ar15 that's fairly accurate. It's 55gr hornady fmj, LC brass and 22.6 gr of 8208xbr. This load is definitely ok the lighter side(2550 fps), which is fine by me since I don't use the AR for anything farther than 200 yards. So as long as its accurate and functional, the lighter the better... Less wear on parts.

Anyways, the only thing that has concerned me is that all the brass comes out with black soot all over where the case head extractor groove is. At first I thought it was just because I occasionally use steel case ammo and the makes the chamber dirty. But I haven't used that in a while and I use a chamber brush to clean the AR , so it's not that.

Is this a problem? This is my first semi automatic I'm reloading for, so I wouldn't even know that maybe its normal( my bolt guns don't do this)

 

[FLIGHT762]

Re: Black powder marks around case head groove .223

The soot is probably due to the light load not expanding the brass cases, fully sealing the chamber and you're getting some gas blow by. I don't think it will hurt anything. Just being very dirty.

Load 10 rounds with a full powder load of 8208 (near 25.0 grains) and see if you get the blackening. I'm betting you won't.

 

[timelinex]

Re: Black powder marks around case head groove .223

Ok I'll try that sometime just to confirm... I suspected the same as you said, but I was under the impression tht light loads leave soot marks on the neck and shoulder, this is way at the bottom of the case.

 

[milo 2.0]

Re: Black powder marks around case head groove .223

It's the gas system, load a mag, shoot 3 or so, drop the mag and look at the unfired one's in it. The top 2-3 will be filthy, just the way things go.

 

[timelinex]

Re: Black powder marks around case head groove .223

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: milo-2</div><div class="ubbcode-body">It's the gas system, load a mag, shoot 3 or so, drop the mag and look at the unfired one's in it. The top 2-3 will be filthy, just the way things go. </div></div>

But it's not that the entire round is dirty. The round itself is relatively fine, but the spot mark I'm talking about is real black. I will check my collection of fired brass and see if I can take a picture.

 

[timelinex]

Re: Black powder marks around case head groove .223

Pictures as promised:

 

[milo 2.0]

Re: Black powder marks around case head groove .223

TL,
I'm going to have to bow out on this one, looks strange to me.
My thoughts, even if it was blowing back from case mouth, the sides would be dirty also How do the primers look?
More thoughts, do you tumble after resizing, or wipe em down?
Lube in the groove could explain the buildup.

 

[timelinex]

Re: Black powder marks around case head groove .223

Usually I ultrasonic clean my brass. However this 223 brass was bought 1x fired and already cleaned and full sized.it's a large scale production, so It's definitely tumbled and not wiped down. I'll check if it's oily there just in case.

EDIT:
ok, I checked the cases and it doesnt seem like there is lube leftover on them, but I can't be 100% sure considering my fingers don't really fit into the groove.

I had an idea of checking some factory ammo cases that I shot a couple months ago. They do not have this mark. I will try shooting a couple of factory rounds next time to confirm this. If so then it has to be load specific. Either the actual load or something with the brass as Milo suggested.

 

[lray]

Re: Black powder marks around case head groove .223

I experienced soot just like that on 30-06 cases that I was loading 'very light' with 125gn flatnose bullets and 9.2gr of TrailBoss. Super light plinking load. I think there's not enough pressure to expand the brass in the chamber... not sure why it just seems to collect in the extractor groove, but it did...