Neck tension nightmare

[60723]

I love a Dasher. Have had good success with a .271 neck using Lapua brass cleaned up 50%. Had a new rifle built with a .272 neck. Started with hydroformed brass from DJ. Fireforming with 30 grain Varget, the rifle shot outstanding and the brass looked fine. Then started a load work up and settled on 32.4g
Varget. Great accuracy BUT saw carbon on the shoulders of every case. Using SAC dies with .002 neck tension. 3rd firing was the same. I anneal every time. Tried virgin brass and same result. Sent dies to SAC and they said everything was correct. Sent rifle back and smith verified.272 neck. He tried more neck tension with hydroformed brass, virgin brass and some turned brass and got no carbon on the necks. MAYBE the mystery is solved. He is still working on it. NEVER had anything like this before.

 

[Tikka6CM]

Why torment yourself like this… when Alpha sells great Dasher brass ready to run straight out of the box after a little chamfering?

 

[JFrank]

Are you annealing virgin brass ?

 

[Tommie]

Paging Mr Guffey

 

[JEFFPPC]

Sounds like it wanted more neck tension.Not a big deal. I never understood, why hydro forming? I have had barrels that wanted either heavy or light neck tension and barrels that shot with either. I think its an area few guys test.Some barrels it turns the light on. Maybe the new no neck, use a mandrel craze of reloading makes it difficult?

 

[60723]

Are you annealing virgin brass ?

Only fired

 

[JFrank]

Only fired

I typically use quite a bit of bullet hold ( neck tension) on my BRA and Dasher and find it much easier to apply and more consistent without annealing at all.
I don’t think alone on this but IDK for sure

 

[Clancy]

Carbon on the shoulder? Ohhhhh noooooo. What will we do???

You lost me at “great accuracy.”

But, more tension and/or less shoulder bump will fix that.

 

[60723]

Shoulder bump minimal. Hope 3-4 neck tension is the solution. Tried not annealing but no help.

 

[Tommie]

Shoulder bump minimal. Hope 3-4 neck tension is the solution. Tried not annealing but no help.

Go with 4. If that helps you know it’s a tension issue and then you can then try 3.

 

[Silo1616]

Shoulder bump minimal. Hope 3-4 neck tension is the solution. Tried not annealing but no help.

I don't have a "Dasher", but on my 30BR the location and shape of the carbon ring has everthing to do with clearance not tension. To tight = solid carbon ring near the top of neck, little more clearance (.0002-.0003) = single sine wave on one side only, little more clearance = sine wave on both sides, too much clearance = it moves down the neck and starts wicking into the shoulder.

 

[Silo1616]

I should add; I dropped from a .324" to a .323" during clearance testing to maintain tension.

 

[Webster]

I love a Dasher. Have had good success with a .271 neck using Lapua brass cleaned up 50%. Had a new rifle built with a .272 neck. Started with hydroformed brass from DJ. Fireforming with 30 grain Varget, the rifle shot outstanding and the brass looked fine. Then started a load work up and settled on 32.4g
Varget. Great accuracy BUT saw carbon on the shoulders of every case. Using SAC dies with .002 neck tension. 3rd firing was the same. I anneal every time. Tried virgin brass and same result. Sent dies to SAC and they said everything was correct. Sent rifle back and smith verified.272 neck. He tried more neck tension with hydroformed brass, virgin brass and some turned brass and got no carbon on the necks. MAYBE the mystery is solved. He is still working on it. NEVER had anything like this before.

Annealing probably has nothing to do with it. How are you annealing? From what i have read on this website carbon on the shoulder means the neck isn't sealing quick enough which I don't understand how that happens. As long as the rifle shoots great why worry about it.

Just searched for other comments on soot.. Several posters say that soot on the necks is from slow powders. Pick a faster powder and it goes away. What powder are you using?

 

[X Count]

Jam your bullets hard and see if it goes away. I had a similar issue caused by too much neck clearance and too long jump. The gas was coming down the case before the neck would expand and seal.

That can also be exacerbated by measuring fired cases that haven't actually blown out to the full chamber length and bumping from that dimension. If it's .003 off of actually touching the chamber and you bump it another .003 you now have .006 clearance. In my case the gas was actually pushing the shoulder back making lengths vary a lot.

 

[ELR LVR]

I have on a couple occasions when starting low
working up a load gotten carbon on the shoulder
I attributed it to not enough pressure to expand the brass tightly to the chamber wall
Min Shoulder bump also
---Bumping the load up slightly- Cured it

 

[L.Sherm]

Go with 4. If that helps you know it’s a tension issue and then you can then try 3.

I wouldnt be afraid to test .005 either.
If annealing isn't doing what you want maybe try not annealing.

 

[DLT]

Carbon on the shoulder? Ohhhhh noooooo. What will we do???

You lost me at “great accuracy.”

But, more tension and/or less shoulder bump will fix that.

I just want to learn in an area I’m not familiar with, why would more neck tension help with carbon coming down the neck ?

 

[Clancy]

I just want to learn in an area I’m not familiar with, why would more neck tension help with carbon coming down the neck ?

More pressure build up before the release. In layman’s terms, the neck will slap open and hit the chamber wall faster allowing less gas (and soot) to blow by.

I run really loose necks compared to most. A little residue on the neck or top of shoulder has never bugged me. It’s nothing I’d be concerned about or give up accuracy over, but less shoulder bump and/or more neck tension decrease or eliminate it.