Excessive carbon on 7mm case? Update.

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 .

So far I've used n560,v150,v160,imr4350,h4831.
Eldx, nosler ballistic tips.
This latest of berger 140 and v160 is the only combo to cause this much fouling.

The only comparison I could get from Vithatori is the 140 Swift A frame which shows a max load of 63.2.

Berger gave me a max load of 66,so it shouldn't be a mild load.
But it didnt feel very stout.
 
45C said:
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 .

So far I've used n560,v150,v160,imr4350,h4831.
Eldx, nosler ballistic tips.
This latest of berger 140 and v160 is the only combo to cause this much fouling.

The only comparison I could get from Vithatori is the 140 Swift A frame which shows a max load of 63.2.

Berger gave me a max load of 66,so it shouldn't be a mild load.
But it didnt feel very stout.
Click to expand...

Interesting ... Looking at powder burn rates for N160 and published loads for powders adjacent to it, if someone had asked me for a recommended Max Load for a 140 gr bullet in the 7mm Rem Mag with N160, I'd have suggested 66.0 grs and an MV of 3000 fps, whatever comes first.
 
Last edited:
I have worked with Vihtavuori N160 quite a bit, and my records have it very close to IMR 4831 as far
as burn rate is concerned. Some charts seem to put it faster, but my experience is as stated. I notice
the Latest Hodgdon chart places N160 as slower than IMR 4831, which does not surprise me. Dave.
 
Last edited:
I disassembled the gun and it was dirty. The chamber was the worst.
I gave it a good scrub.

I'm going to load 5 rnds,using the cases from the same lot
And load them at 63 g.
That way,I can rule out if the dirty chamber was the culprit.

If they still come out all fouled up,then I'll try new brass,see if that's the problem.
 
Just a thought, but if the cartridges just came out of a warm truck directly into sub 0 temp,is it possible for condensation to build up on the brass,
Allowing the now wet brass to get the carbon all over it?
 
Negative - the carbon wouldnt be there in the first place if the brass was filling the chamber. With 6 reloads, your brass is getting work hardened. Couple that with (perhaps) overzealous FL sizing, and you may have the cause to your problem. You could eliminate this possibility by partially resizing your brass, neck sizing your brass, or using new brass. I would be tempted to go with new brass at this point, as you are running the risk of a case separation.
 
Last edited:
45C said:
I disassembled the gun and it was dirty. The chamber was the worst.
I gave it a good scrub.

I'm going to load 5 rnds,using the cases from the same lot
And load them at 63 g.
That way,I can rule out if the dirty chamber was the culprit.

If they still come out all fouled up,then I'll try new brass,see if that's the problem.
Click to expand...

I would expect those to come in at about 2900 fps at a pressure of about 50K psi, which should be enough to seal the neck. If your MV's are much below that, the powder you're using would seem to be slower than first thought.

I like to minimally size and anneal my brass every five shots. That has pretty much eliminated split necks, with primer pockets going first since I tend to load at or near max loads.
 
Obtaining 6 loads out of 7 Rem Mag brass is already a feat in itself. You brass need annealing or better replacing.
They are not sealing against the chamber wall. Brass is too hard.
I would clean the chamber very well and use new brass. Your problem will go away.

A simple test if you need convincing..clean chamber and shoot a few factory load..
 
Last edited:
The best powder I've found for the 140gr in the 7 Rem mag is N165.................won't hunt with" Burgers" for personal reasons I haven't the time to get into.
 
mbogo3 said:
The best powder I've found for the 140gr in the 7 Rem mag is N165.................won't hunt with" Burgers" for personal reasons I haven't the time to get into.
Click to expand...
There not my favourite, I prefer the 150 Nosler B tip.

But I have 150 pieces of berger and the nosler 140 g is rarer than hens teeth.
 
Maybe I could skip testing the existing brass and go with the once fired,FL resized brass, that I just bought?
 
45C said:
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.
Click to expand...

Looks like there is sizing lube on the cases. Could that prevent a poor seal and the carbon mess?
 
Buckmastr said:
Looks like there is sizing lube on the cases. Could that prevent a poor seal and the carbon mess?
Click to expand...
I always wet tumble after sizing,its not lubes.
It's the carbon smeared over them after extraction.
It was kinda wet,I guess from going from extreme cold to extreme hot?
 
Lead hammer said:
Are you sure your scale is accurate?
Click to expand...
Funny you should ask.
I checked it with a Canadian dime and it was right on.

Rechecked with a Canadian nickel and it was off 5 g.
I'm going to try a few other options tonight.

But the case case capacity looks right.
 
45C said:
Funny you should ask.
I checked it with a Canadian dime and it was right on.

Rechecked with a Canadian nickel and it was off 5 g.
I'm going to try a few other options tonight.


But the case case capacity looks right.
Click to expand...

Check it with 20 bullets of known weight. See what the average is. I use RCBS check weights, however if a bullet is 130 grains, it should weigh close to it. 129, 131 for example. You could weight the same 20 bullets on another persons scale to see how far off it is or isn't as well.
 
Lead hammer said:
Check it with 20 bullets of known weight. See what the average is. I use RCBS check weights, however if a bullet is 130 grains, it should weigh close to it. 129, 131 for example. You could weight the same 20 bullets on another persons scale to see how far off it is or isn't as well.
Click to expand...

I weighed 20 130 g eld-m, they were all 130.1
 
You must log in or register to reply here.
Back
Top Bottom