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Neck tension nightmare

60723

Gold $$ Contributor
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.
 
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?
 
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.
 
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?
 
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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.
 
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
 

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