Smokey Shoulders

[Mudflap621]

Why am I getting smokey shoulders on two different BRA chambered barrels?

My first barrel the dimensions were a touch off so I just figured it had something to do with that.

Now with a new barrel I’m seeing the same thing. First firing of Lapua all necks seem to seal up tight with no carbon on shoulder. I went and checked some speeds with once fired and sure as shot they all have carbon down the shoulder.

Virgin Lapua was running 2750-2760
Once fired I went from 2785-2850 all showing Smokey shoulder.

Brass prep went as follows:

Amp annealed
SAC modular w/ .263” bushing and .2405” mandrel

Shoulder was not pushed back on these as they chambered w/o resistance.

 

[Mudflap621]

 

[Dolomite]

I get the oppposite results the non annealed cases have carbon on the shoulder.

You use a .243 bushing? What is your loaded round?

 

[Mudflap621]

I get the oppposite results the non annealed cases have carbon on the shoulder.

You use a .243 bushing? What is your loaded round?

I could understand the sooted shoulder if they weren’t getting annealed.

Correction it’s a .263” bushing followed by a .2405” mandrel, shooting for .003” neck tension.

Loaded rounds measure .2685” -. 269”

My last barrel I ran a honed .246” Forster followed by a .241 mandrel and saw the same thing.

 

[Aftermath]

How much jump?
Try a few with the bullet at or real close to the lands.

 

[Mudflap621]

How much jump?
Try a few with the bullet at or real close to the lands.

Jumping .060”, I could test closer but it’s not preferable.

 

[Dolomite]

I’m about .020 off the lands. I ran the speed up and down testing and still have carbon on the shoulders of annealed brass. I have a .272 chamber running .268 loaded round.

Could it be more neck clearance?

 

[spife7980]

It’s fine. If they shoot how you want them to then don’t worry about it.

 

[Mudflap621]

It’s fine. If they shoot how you want them to then don’t worry about it.

Was more curious as to if maybe it was something in my process creating it that I could remedy.

We’ll find out shortly as just reached 200 rounds and going to start testing loads, but fireforming showed a lot of promise.

 

[RTH1800]

In general smoked necks/shoulders are due to too much shoulder bump, too much neck clearance or too low pressure.

 

[Mudflap621]

In general smoked necks/shoulders are due to too much shoulder bump, too much neck clearance or too low pressure.

I’m assuming this chamber has a .274 neck as my fired cases are coming in around .273-.2735.

Shoulders are all within .002”

Guess I was just hoping the new chamber would be different is all.

I’m assuming the crush fit of virgin br brass was helping with keeping things sealed up but I’m not going to shoot brass w/o any bump. I tend to favor .002”- .003”

 

[FredHammer]

I think it’s a combo of neck clearance and powder pressure type/spike. It’s nice when it’s not present. I’ve lived with it for some bug hole loads.

 

[Hardshot]

I have the same problem if I go more than 2 firings without annealing on Lapua brass . Alpha brass doesn’t have the same . Issue? My smith at well re known benchrest builder took my reamer and went in .003 more by hand to maybe clean up the shoulder neck , made no difference ! I don’t know what else to try

 

[Hardshot]

I think it’s a combo of neck clearance and powder pressure type/spike. It’s nice when it’s not present. I’ve lived with it for some bug hole loads.

Well I’m having the exact same issues with Lapua brass . Third firing and soot big time . I turn necks but I don’t see .003 “ less in the chamber a issue. I have tried different dies , less bump , jammed bullets nothing changes unless I annealed the brass . It’s only good for one firing then have to anneal . Tried 5 Alpha brass a buddy gave me and no soot . Even after 5 firings. I don’t get why the Lapua is doing this ? I sure could use someone else cure for this issue. I m using N-150 but Varget does the same

 

[Dolomite]

First firing of Lapua brass probably had more neck tension which most likely caused it to seal off the chamber better when fired.

Try sizing 50-75% of the neck only on your Lapua brass and see what happens. Or increase the neck tension to create more pressure to fully expand the necks on firing.

 

[918v]

Well I’m having the exact same issues with Lapua brass . Third firing and soot big time . I turn necks but I don’t see .003 “ less in the chamber a issue. I have tried different dies , less bump , jammed bullets nothing changes unless I annealed the brass . It’s only good for one firing then have to anneal . Tried 5 Alpha brass a buddy gave me and no soot . Even after 5 firings. I don’t get why the Lapua is doing this ? I sure could use someone else cure for this issue. I m using N-150 but Varget does the same

Maybe Alpha brass is softer from the start. So after 5 firings it is at the hardness of new Lapua. Also could be neck clearance as well, less on alpha cases, so brass doesn’t move as much during firing.

 

[Hardshot]

Maybe Alpha brass is softer from the start. So after 5 firings it is at the hardness of new Lapua. Also could be neck clearance as well, less on alpha cases, so brass doesn’t move as much during firing.

First off thank you for sharing any insights.
My Lapua and Alpha are both neck cut to just clean up the necks ,.013 “ is the wall thickness on both cases. Loaded rounds both measure.269 I have a .272 Chamber leaving me .003 of expansion . I bump them .002 ” that how far at a minimum to get the web sized .
As for hardness I don’t have any special way of measuring hardness other than the Alpha hasn’t been annealed yet after 5 firings , as a experiment between the two manufacturers.
Puzzled, 55 years of shooting and reloading and this is the first thing that I couldn’t learn info on to overcome.

 

[acudaowner]

a little brasso some 0000 steel wool and you will see nothing but shiny brass it also makes cracks stand out if and when you ever get them