Excessive carbon on 7mm case? Update.

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45C

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Hey
I'm getting an excessive amount of carbon on my 7mm rem mag cases .
I'm using Vithatori 160.
The carbon is all over the case and really thick,between the belt and the breach face.
Any thoughts?
This is with start load to max load.
All cases are a bit short , at 2.470.
No crimp.
6 timesvfired brass, first time using berger bullets.
Two batches,one at 3.290 Col and one at 3.390.

I found the best 5 round group ( sub moa) with 3.290 which was book recommended col.

The 3.290 which was 20 though off the lands,didnt to to well.
 
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Ganderite said:
Pressure too mild?
Click to expand...

I dont think so as I loaded from min loads
All the way to max.
Start 59 g
Max 66 g
Vithatori 160
I loaded 5 rounds per weight.
Four , five round batches at 3.290
Four , five round batches at 3.390.

This was the shortest brass I've used,at 2.470.
And it was the first time using this combo.
Every piece of brass had Corbin smudged all over the case, and a build up between the belt and breach face
 
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I did use a very slight crimp, but is it possible that the brass is to worn out,causing it not to have enough neck tension?
 
Or is it possible, its carbon buildup left from my last session?
Last time out I put about 80 rnds through it and didnt clean the gun
 
I believe in your rifle, with that powder and bullet, you are still dealing with low pressures.
Almost invariably, when there is soot [carbon] on the outside of the case, the pressures are
low, preventing a good seal up at the neck area. Dave.
 
The only time I experienced carbon as such was with low pressures. I remember loading a Nosler 150 gr. Ballistic tip with IMR4831 with 55.0 grains in my 30-06. Although it was a most accurate load, I just couldn't use it, not safe.
 
I'll check the speed next week end.
I'll start at 64 g ,which produced the most accurate group and keep working up.

I should add that I got this data from Berger.
They haven't got it listed yet but are planning on adding it to there next book.
 
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track said:
The only time I experienced carbon as such was with low pressures. I remember loading a Nosler 150 gr. Ballistic tip with IMR4831 with 55.0 grains in my 30-06. Although it was a most accurate load, I just couldn't use it, not safe.
Click to expand...

Interesting.. I've had the same problem with IMR4831 under 70 gr Match Kings in a 243 Tikka. It's a moderate load, 44.7 gr of powder if I remember right. Around 3150 fps.

The really interesting part was that it wasn't like that from the get-go.
For the first couple of years that I used the load it was slightly sooty in the neck area, but nothing unusual.

Then all of a sudden it went to hell. Still accurate, but worse soot than 45C's loads, all the way back to the case head and into the extractor groove of the case.

I stopped using the recipe after a couple of sooty range trips.

It wasn't the brass, I reloaded them with N150 and 90 gr Bergers and they're fine.

The only thing I can think of is that the powder was starting to degrade.
 
That's a classic low pressure indicator, but since you're using published max loads and chronographing at expected MV's, I would definitely not keep adding powder in the hope that the "problem" will go away. Are there any other possible causes? Cavernous chamber for example? If it was very hard brass, you'd expect cracks at some point. Interested to see how this goes.
 
Eagleye said:
I believe in your rifle, with that powder and bullet, you are still dealing with low pressures.
Almost invariably, when there is soot [carbon] on the outside of the case, the pressures are
low, preventing a good seal up at the neck area. Dave.
Click to expand...

The case is not sealing, that's obvious. And carbon is incompletely burned powder.

So "probably" low pressure but not necessarily. A damaged ((gouged, pitted, etc)or very filthy chamber can also prevent the case sealing properly.

OP has so much carbon I wouldn't keep shooting that load until I discovered how it is happening.

Clean the rifle and esp the chamber really well and inspect for damages. Double check the load. If everything is as it should be with the rifle, and the load is proper, then the powder is misidentified, or going bad, or just not suitable. Stop using it.
 
Are you full length sizing? Perhaps you're pushing the case shoulder back too far and it's not sealing up letting carbon blow back. Are you annealing your brass? If not it's probably getting very hard further exemplifying the issue.
 
If it is full pressure loads as OP says the case would fireform regardless where the shoulder was. Cases can leak with chamber pressure below 35-40k psi range. If it's not making full pressure then why not? That's the big question.

I would be looking for a mechanical issue first after a good cleaning. If nothing showed up the next step would be changing powders.

One other thought - is the rifle a semiauto? That would help explain carbon buildup. I assumed it was a bolt action.
 
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The rifle is a browning xbolt with approximately 400 rnds through it.
This is the first time this has happened with 3 different powders.
The brass has been loaded approximately 6 times.
Full lenght sized each time.
With the only issue being,its getting shorter each firing.
No cracks etc.
No annealing.
I got the data directly from berger.
63 start 66 max.
No pressure signs at all.
The 66 max load felt light,with hardly any recoil.
Berger did say that this is a new combo for them,and they are currently still working on it.
I have Hornady tools on the way,to correctly measure the cases.
I also have a bunch of once fired brass,that I'm going to annealing and start using.
I have a new chronograph on the way and will check the speed as well.
As this is a new bullet/ powder combo,I'm not sure what the case is.
This is some of the cases.
 
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Andy said:
That's a classic low pressure indicator, but since you're using published max loads and chronographing at expected MV's, I would definitely not keep adding powder in the hope that the "problem" will go away. Are there any other possible causes? Cavernous chamber for example? If it was very hard brass, you'd expect cracks at some point. Interested to see how this goes.
Click to expand...

It's not published loads yet.
Berger said they are working on it and will be adding it to their next book.
I haven't chronied them yet, but will on Wednesday
 
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