Black soot build up on case heads

[milo-2]

IMO, you really need to clean your chamber if gas has been escaping. I use a bigger brush, 338, then cut a 1 1/4" circle of scotchbrite with some C4 on it, chuck your rod up in a drill and spin it, then wipe it out.
Do you have a borescope?

 

[ShtrRdy]

Ok, that means you have gas coming back towards you, your necks and or shoulders are not sealing off. The sides of your cases shoot have some carbon on them too.
I would look into this right now.

I dunno about that. The primer is pretty flat already.

 

[243winxb]

To get soot on the case head, the body and neck should have soot? Like here- https://thefiringline.com/forums/showthread.php?t=476535

Or is the primer backing out on firing & then reseating? Coating the Head? If its even possible?

 

[Taco John]

How muck gunk on the bolt face?

 

[Gwine]

Are you sure that is carbon from being fired. Is there something on the bolt face that is transferring to the brass when fired? From the looks of your case, I don't see why there would be carbon on the case head.

 

[DBoone]

Example. This is after being in the tumbler for a bit too

By chance are you using a wet tumbler?

 

[Jakeweb09]

IMO, you really need

By chance are you using a wet tumbler?

No.

 

[Jakeweb09]

Are you sure that is carbon from being fired. Is there something on the bolt face that is transferring to the brass when fired? From the looks of your case, I don't see why there would be carbon on the case head.

This thought has crossed my mind. It's a custom build with a Stiller action, and the whole thing was coated.

 

[Jakeweb09]

To get soot on the case head, the body and neck should have soot? Like here- https://thefiringline.com/forums/showthread.php?t=476535
View attachment 203386

Or is the primer backing out on firing & then reseating? Coating the Head? If its even possible?

yeah cases don't look like that at all. Tiny bit on necks but none on the body

 

[Farmerboy78]

What coating is on the bolt face? Is it oily?

 

[Backcountry sports]

Anyone ever get it? And what causes it? I've been getting decent build up on some cases but not all. Tried multiple primers and same thing. It's happening on a 7 Saum with ADG brass and reloader 26.

I shoot the same with reloader 22 no soot very clean

 

[doggonner]

this could be gas escaping around the primer high pressure...watch out when I get black on the case head I investigate to see if it went up the pocket wall and squeezed out between the pocket and the primer high pressure be safe..are the pockets tight or loose if loose throw the brass away and get new brass and back off the load..if it will not come off it's gas do you have erosion on the bolt face

 

[doggonner]

7:00 and 12:00 look like pressure leaks on the case head but I could be seeing things

 

[7070yshot]

Anyone ever get it? And what causes it? I've been getting decent build up on some cases but not all. Tried multiple primers and same thing. It's happening on a 7 Saum with ADG brass and reloader 26.

Yes, I get this for a couple of reasons. In no particular order

1 - poor quality brass
2 - primers seared too deep or slightly crushed when being seated - primer pockets need to be uniformed depth
3 - blow back from chamber being in poor condition of some kind.