My 6mm ARC with a suppressor ejects really sooty cases. But, it feeds and ejects flawlessly.

Is this just due to the added backpressure from the suppressor?

Is there any load adjustment that I could/should make for this?

Shoot it without a suppressor and see the difference??

Some loads made for suppressors are low velocity and might do that.

Yes, suppressed rifles produce more soot than unsuppressed. You can try different powders as some might be cleaner than others. I shoot around 7-8 thousand suppressed rounds per year (only one AR type, most bolt action) and they are dirtier. Especially AR type.

No question, suppressed rifle barrels get dirtier, faster. Also seen accuracy drop off when the dirtiness loading reached the critical level ( but took 100 + shots to get there ) after which thorough suppressor, action and barrel cleaning got accuracy back on track.

Something else I noticed with suppressors.

The barrels heat much faster.

Thanks guys. I was using CFE223, which they say stands for Copper Fouling Eraser but I think that it stands for Carbon Fouling Extreme.

This is my first year shooting suppressors. I used to live in the communist country of California, so I'm on a steep learning curve.

The first thing that I learned was not to touch the suppressor directly after firing a dozen rounds through it.