Thread: Sooty Necks

What causes sooty necks on the cases?

I thought it was something to do with not enough pressure sealing the neck in the chamber on firing?

I did a ladder test the other day and the necks were all quite dirty after firing. Some of the loads were over book max as I had found no pressure in the previous ladder test.
On the last load I had a bit of trouble opening the bolt and had a flat'ish primer, so know thats over loaded for me. But it was still sooty.
Powder is AR2217 in a 270wsm.

Thoughts...

Dirty chamber from the initial low loads?
Suppressor pushing dirty gas back after case has shrunk back?

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is it a problem?
I get it on my cases too but it dosent faze me,

I get it with all my hand loads

If your getting residue on your neck with your max load, it can just the diff between chamber and case neck dimentions. The case neck is not obturating or it is returning to size as the gasses settle. Usually shows around a 5 thou difference. You can get it with or without a suppressor.
I dont think it is a problem if you are near max powder load as long as it shows no further than the necks.
I get it in varing degrees throughout several cals and the only major difference is neck clearance. Worse in lots of clearance, less in little.

A sooty inside color can indicate an inefficient burn of the powder. BUT, that could be for several reasons. It could be from a powder that burns too slowly, a very light powder load of the correct powder, or other causes. IMHO, the root cause is low chamber pressure.

However, you should be aware that sooty cases ranks right up there with fired primers as being no more than "a general indicator". It is NOT exact in any manner, shape, or form. Nor should you use it as a reliable reference in place of chrono data.

Having said that, let me say also that I'm not aware of any fuel (wood, coal, kerosine, nat gas, gasoline, or smokeless powder) that is sooty when it's burning efficiently.


A sooty exterior can indicate not enough chamber pressure to properly expand the brass.

Cam, No suppressor so can't be that. Also if I chamber a loaded case and extract it there is no sooty marks

Originally Posted by Bill999

is it a problem?
I get it on my cases too but it dosent faze me,

I was under the impression that having sooty necks was one of the signs of low chamber pressures

Can't be if my over max loads do it too

Originally Posted by R93

If your getting residue on your neck with your max load, it can just the diff between chamber and case neck dimentions. The case neck is not obturating or it is returning to size as the gasses settle. Usually shows around a 5 thou difference. You can get it with or without a suppressor.
I dont think it is a problem if you are near max powder load as long as it shows no further than the necks.
I get it in varing degrees throughout several cals and the only major difference is neck clearance. Worse in lots of clearance, less in little.

Ok so my neck clearance in the chamber might be quite high. I think I can live with that, Something to do with being a Tikka I suppose. I was just wondering if there was something I was doing wrong perhaps.
The fact it doesn't go up the shoulder is comforting, as I'm not real keen on a face lift with hot gasses.

Sakkaranz,
The soot is around the outside of the necks and a dark black colour.

Not high, puku just not as tight as some custom chambers as far as neck clearance goes. Pretty sure I get it on all my reloads. I can wipe it off with a rag easy enough and never really addressed or worried about it.
I get it on my .260 imp cases but in saying that, it has a very low ES and I get 9-10 uses of a case before I consider forming a new one. So it cant be anything to be concerned about.
Could be other things as well. I notice a change using different powders and even in a change in primer, maybe leading on to what sakkaranz says about efficiency.

For anyone interested this how the ladder test went.


Aiming point was the top right corner of the box. First shot 1/4" right, Second shot 1/4" low, Third shot 1/3" high and left. Forth shot out right, then fifth shot low 1" and right 1 1/2".
The two other shots were from some other shooting.
Slight pressure signs were in shot four. And I had trouble opening the bolt on final load.

Fuck how the hell did that turn around. Fucking stupid computer

Originally Posted by sakkaranz

Having said that, let me say also that I'm not aware of any fuel (wood, coal, kerosine, nat gas, gasoline, or smokeless powder) that is sooty when it's burning efficiently.

It won't be soot, just the same carbon you scrub out of the barrel.

What range was the ladder test shot at - I do mine at 300 or so and the holes are never that close together (crappy old Mauser's - ya all can say it!).

It was a shade under 300m, a bit closer to 100m to tell you the truth.
Once I pick out a weight ill play at longer distance when changing OAL