Carbon around case necks?

[Luke2K5]

I did some shooting earlier today. Shot some 243 reloads out of a new bolt action Savage rifle. All went well with performance and accuracy. According to my chrono, the loads were fairly consistent and well within safe range. The case necks were blackened with varying degrees of carbon. What would cause this? All of the cases were properly sized and the bullets were seated precisely where they should be.

L2K5

 

[rbernie]

When this happens to me, I generally also find that the OD of the case necks are no longer nice and smooth and consistent. I fugure that this all implies that the neck isn't completely sealing against the chamber walls. It doesn't seem to hurt much of anything, and I've not yet tried turning the case necks to address this.

 

[kimbernut]

Carbon on o/s cartridge necks

I've noticed this on quite a few different bottle necked cartridges-both handloads and factory .223 Rem through .300 Win.Mag. I'm sure it's just the neck not sealing against the chamber walls as rbernie has mentioned but like him also I don't see it as a detriment to accuracy or velocity as best I can tell.Before tumbling I'll twist the case neck in a ball of 2 or 3 ought steel wool to remove it. If anyone can give us any preventative tips I'd sure be interested.

 

[Luke2K5]

Thanks for the info. I noticed on the new brass (factory 243 ammo) there was moderate carbon on just one side of the neck but on reloads it was 360 degrees and heavier. And it was much more than I've noticed from time to time on other rounds I've fired. So maybe it's a combo of the cartriges and the gun.

Thx again.

Luke2K5

 

[mete]

I guess you've never seen a case from a HK G3 series which has a fluted chamber . The gas escapes along the flutes and you get carbon stripes on the neck and shoulder !!