Soot On Case Bodies

What's happening is I'm getting soot down the length of the case, sometimes all the way to the bolt. Normally I just see soot on the neck and shoulder. Is it a problem?

Some information:
The cases are Norma 6.5x55. They have been fired 8 times with no annealing. The shoulder is bumped back 0.002-0.004" on resizing. The load is 49gr of AR2213SC with a 120gr projectile. The estimated pressure is 3245bar with the max for the 6.5x55 SE being 3800bar.

I have several theories as to why this is happening:
The pressure build up is too slow, allowing some initial blow by.
The cases are too hard to seal correctly.
The shoulder bump is too much for the cases.

Thanks for any input.

Im GUESSING to light of load..so its not sealing properly...has it done it through all 8 loadings??? does it do it with other loadings????
does rifle do it with factory loads????
do you use magnum primers??? they are sometimes recomended for AR 2213sc..well they were at one stage for many loads...why I use them for everything except subsonic....

Have they been annealed ?
Do you full length size every load ?
As MD says, looks like blow by
I assume factory loads are ok ?

It did do it while I was doing some incremental testing with 2209. But it didn't seem consistent. There is a small amount of soot on the neck of the factory rounds (Hornady Superformance).

The primers are Federal 210. My '96 ADI manual mentions magnum primers with 2213 but the modern ones don't. I do know it's an incomplete burn ~86%.

The cases have never been annealed and are full length sized each time.

The only way that can happen is a failure of the case to seal...I think it is springing back too quick from the initial firing, allowing gas to flow back (with soot). Surprising as would think 49gn isn't a light load. I'd try magnum primers as suggested... but if you send me your brass I can anneal it for you in an AMP...drop me a line if you want to try that.

hhhmmmmm @gundoc what say you oh great n wise one???? oversize /loose neck area??? or load may need to upped a LITTLE ???

I recon its the 8 loads without anealling and a light load.
Dam good chamber clean and try with annealed or new brass.

I dont think your shoulder bump is excessive or would cause it.

It looks like you are using a suppressor in which case the sooting is a normal by-product caused by a higher residual bore pressure after the shot has left the barrel and is nothing to be concerned about.

Quote:

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Originally Posted by gundoc

It looks like you are using a suppressor in which case the sooting is a normal by-product caused by a higher residual bore pressure after the shot has left the barrel and is nothing to be concerned about.

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Looks like I forgot to mention the most important part, the suppressor. Thanks for the help.

I had this exact issue with a brand of suppressor, it was a heavy, over barrel fully enclosed stainless job ,I was using Lapua cases and Vihtavuori.
Couldn't figure it out.
Didn't seem to affect anything just looked ugly, anyway I sold the suppressor [not for that reason but to buy a muzzle forward A-Tec] and the issue went away as well.

Greetings Magnetite,
Additional to the above replies I believe that AR2213SC is too slow for the 120 grain projectile. You would likely have less trouble with AR2209. Current manufacture AR2209 (post 2,000) is faster than the lot used by Hodgdon but you can still use their max which was for low pressure. Work up though.
Regards Grandpamac.

Quote:

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Originally Posted by grandpamac

Greetings Magnetite,
Additional to the above replies I believe that AR2213SC is too slow for the 120 grain projectile. You would likely have less trouble with AR2209. Current manufacture AR2209 (post 2,000) is faster than the lot used by Hodgdon but you can still use their max which was for low pressure. Work up though.
Regards Grandpamac.

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I’m currently working up a load for the 120s with 2209 and 2213sc to compare. 2213sc has the allure of accuracy.

From what I understand too slow of a powder won’t burn fully, or won’t allow the desired pressure to be reached. Are there any other caveats to be aware of?

Quote:

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Originally Posted by Magnetite

I’m currently working up a load for the 120s with 2209 and 2213sc to compare. 2213sc has the allure of accuracy.

From what I understand too slow of a powder won’t burn fully, or won’t allow the desired pressure to be reached. Are there any other caveats to be aware of?

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Greetings Again,
The powder all burns in the barrel in spite of what some believe so the problem with AR2213SC is you can't get enough in the case to develop the velocity. Hodgdon gives a load of 49.5 grains with the 120 at quite low pressure. Nosler lists 51 grains from memory behind the 125 grain, probably at max pressure. With AR2209 Hodgdons lists 46 grains of the older and slower lots of AR2209 giving around 2,800 fps. My chronographing agreed with this. I loaded 46 grains of the current AR2209 behind 120 grain Speer projectiles which chronographed 2,870 fps and was accurate. Much of the 6.5 x 55 data is light due to the Norwegian Krag rifles chambered for it so getting good data is tricky. My rifle is a T3 with a 570mm barrel. My current load is with AR2209, late lot, 45.5 or 46 grains behind the 129 grain SST giving 2,800 or 2,850 fps. Have not decided on which one yet.

I suspect that your old cases are part of the problem and need to be annealed. I anneal after 3 loads, some do it every load.
Regards Grandpamac.

Quote:

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Originally Posted by gundoc

It looks like you are using a suppressor in which case the sooting is a normal by-product caused by a higher residual bore pressure after the shot has left the barrel and is nothing to be concerned about.

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Ah, that explains why my AR soots up the cases

The ar gas operating system designed by stoner used a variation of the direct gas impingement system best known in the jungmans mag 42 b. Suppressors often caused over gassing hence the use of ajustable gas blocks.
Irrespective the system was intrinsically dirtier than a gas piston actuated operating system.
Thankfully the anguish of having to clean all your dirty brass has being removed by our caring government and we are all safer as a result.