Cob Collected Some "Gunk"

I might suspect really goopy aromatic blends, but not 1Q or anything similar. I have the same MM cob, and though it has a dark finish on the cob, I don't see it making it through the wall into the chamber. It's pretty settled and dry. This is a mystery to be solved. Post again should you find the offending substance.

It could just be a function of build up over time. After smoking a cob for a few bowls, take a pipe cleaner and double it up and run it through the shank into the bowl.You'd be surprised what crap you get out...

I always wipe out cobs and meers with unscented baby wipes. No remaining tobacco residue whatsoever.

The bottom of a cob pipe is not smooth, and there is a lot of area for gunk go accumulate. Even a dry-ish tobacco, if smoked hot, can cause moisture at the bottom of the bowl of any pipe. I use Czech tools when I smoke, and after smoking a cob, you can use the little metal rod on the Czech tool to dig out extra pieces of baccy down on the bottom of the bowl below the shank.
Also, cobs need rest. You can smoke em much harder than briars, but their absorbing ability is finite, and they'll eventually get sour. It might be the wood shank that needs rest more so than the cob material itself, but anyhow, they do benefit from a good break. Thats why I have so many of them, and usually keep a couple of new ones on hand as well ::

What Lawdawg said.

After every couple of smokes in a cob, I fold up a paper towel, dab it with some 190 proof grain liquor, and stuff it down in the bowl and twist it around, almost like a light reaming. Combined with proper rest, that really freshens up and cleans a cob, and keeps it from forming a cake so it will retain its absorbing properties (disclaimer: some people like cakes in their cobs, some don't - It's personal preference)
I know that 190 proof liquor isn't available everywhere you might go, but even if it is not available in your area, my recommendation would be to find the nearest place where it is (even if hours away), and pick yourself up several bottles. I dip pipe cleaners in it to swab shanks, and I use it to wipe out bowls. It's the only "cleaner" I use for pipe cleaning, it works great, and one bottles lasts me a very long time, more than a year.
Another old trick I learned on this board, which I will do with particularly sour over-smoked cobs (after cleaning with alcohol and letting them dry out) is setting them out in the sun. For one reason or another, that seems to freshen them up quite a bit. I'm not sure of the causation (whether its the heat, the sunlight, or just good air circulation), but it works. Important to note: remove the plastic stem and do not set it in the sun. I've "sunned" cobs before with both plastic and acrylic stems left in, and the "tenon" sometimes will get warped so that it doesn't fit in the shank properly.

Do they still leave behind a residue at all, even if they have no smell?

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I've done that for years with no I'll effect. You can also use a wet paper towel.

Every so often I use my pocket knife to lightly ream the chamber on my cobs if I notice the cake becoming soft.

You can even use an old butter knife if you don't trust yourself with sharp things in the bowl. But however you do it, get that soft stuff out of there. That's where nastiness resides, and after a while, you'll start to taste it.

I wipe out all my pipes with a paper towel/napkin after scooping out the ash, don't build cake, and therefore don't ream. The carbon layer still does its job. I have quite a few pipes, so they dry out pretty well "resting." I've never run into any residue in my cobs, over years. So I still think this gunk has a distinct cause and is not a characteristic cob thing. Let us know if anything further surfaces on this phenomenon. It sounds different.

Is this just a tar accumulation that you're talking about?

I don't have cake in my cobs per se because I also wipe out the pipe bowls but the walls can still acquire a tarry accumulation that becomes sticky with exposure to heat. I assume that's just the nature of the beast as we are combusting tobacco in them after all.
I'm not sure if what you are observing is the same thing that I have observed. Any chance of a picture?

Rereading this thread these thoughts

came across.
First thought was it could be years that have settled around the shank overtime.

Thought number two, since you started you smoke Aros It could be the result of the chemicals that are used to carry the flavors are not burning off. Along with that the tobacco could be to wet.

I've got a Czech tool and also use an old style 'nut pick' to get to the dottle at the bottom of my cobs.

I develop some cake, and eventually use one of my reamers on 'em. Never had a problem using a reamer on my well broken in cobs. Dry cakes breaks off readily, and allows for moar baccy.

With the typically open draw of a filter cob w/o using a filter, it's easy to generate moisture via the combustion process, so, you keep that in mind as you smoke those.

The nut pick has a slight curved end that helps pick and pull.