I think I know the answer to this but thought it would be a good question for the board....and to see if I am wrong! Would the sooty cases be coming from a light load not sealing the case against the chamber walls and allowing blow-by?? If that is the case it would also explain the lower than expected velocities.

The caliber I am shooting is a .30 Gibbs.

Any and all input is appreciated.

Depends on how low you are going and whether you are using blackpowder or smokless...

Try a little faster powder...or start using a medium-heavy crimp.

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It's not only that low pressure does not widen the case sufficiently.
The combustion process is different to a full load thus leaving more unburnt residue (soot).

be carefull about determining the cause of the low pressure. A bad batch of powder could be the cause. If it were, and you compensated by increasing the load, guess whats going to happen when you buy a new batch of powder!
So could too light a bullet, and a number of other issues. Think it through.

Thanks for the input. I am right on with the bullet and powder......168gr MK's and RL-22. The powder is a good lot...I use the same canister in my 280 Imp and 6.5-06 with no problems. I highly suspect a light load because I am working with a cartridge that has virtually no load data. I wanted to start reasonably low (but not low enough to get into trouble) and work up. That is also the #1 reason for getting a chrony before getting head on into load development.

Right now it is loafing the 168's along at 2700fps. Thanks for the input fellas.

Danb I would suggest you use a faster burning powder for your fireforming. 3031 or 4895 are favorite powders of mine for fireforming. They tend to burn cleaner even @ lower pressures than the slow burning powders such as 4350,4831.RL 22&7828.

Snowman.....the forming loads wer shot with Varget and bulk 165's. They formed great and sealed the chamber nicely....no soot. These loads I am discussing now are the loads used for development.

Sounds like you need more powder!

Danb You may have a couple contributing factors to the sooty necks. As Johnny has indicated you need to increase your starting load. The other thing is that after fireforming you have work hardened the cases. With work hardened necks you may be within a couple grains of max before you get the necks to seal.You may want to anneal the necks.