It seems that my issue may indeed have been the Green Colorant. (which is odd, because i went green to red, back to green ALL slow extrusion...)

I spent 5 days @ ~5 hours a day Extruding at the incredible slow rate with nothing but Virgin MG-94 (no colorant).  it was VERY slow for quite some time... but after about 100m of natural/white, it finally seems to have Kicked 'er into overdrive, and is back at the fast speed.

So all told, things I did that affected this:
Took off nozzle and replaced (reminds me... i need to clean and re-attach my melt-filter nozzle...)
Dug some goop out of the barrel - hot end with needlenose pliers while nozzle was off
Ran thrugh enough bull%*($% to Finally cleanse it

Its going GREAT now

Might be far too much work in light of what you'd charge for a barrel replacement, but thought it was worthy of asking.

Might it be possible that ive Polished the inside of my barrel enough through usage that im not getting enough Friction?

I won't rule anything out, but I have run 250lbs (roughly 50 gallons) of ABS before experiencing my first and only stoppage of output, and then ran another 50 pounds since then with only a cleanout performed, same parts - so I doubt you've polished anything, though some other factor may have changed the surface quality.

One other thing to try is fully insulating the entire barrel, if you haven't already. That should improve output on both normal and reduced output conditions.

I know this isn't the answer you want, but its really hard to say what the course of action should be because I have so little experience with it, and can't seem to replicate the problem.

You can try running virgin material first, no harm in that. What diameter are you seeing?

How much material have you extruded so far? All ABS?

hey, "im not sure" is a prefectly valid answer!

im going to give it a try with virgin material, i guess i cant really call it a Purge, but i will Flush it through with uncolored pellets, and see what happens.

Ive probably put through about 1-1.5 Gallons of pellets so far? (i store it in a 5gallon pail with Desiccant...)   Im still getting a pretty consistent 1.67-1.68mm filament coming out, just slowly.

Might it be possible that ive Polished the inside of my barrel enough through usage that im not getting enough Friction?

You can give this stuff a try, and see if it cleans everything out-

http://www.ebay.com/itm/ASACLEAN-PURGIN … 4d207f158a

I'm fairly sure this is what the nozzle cleaning filament is made of. 

When I had this problem, only replacing the barrel seemed to work.  Maybe there is something that changes in the surface of the barrel that reduces the friction.  If you get a new barrel, it might be worth cutting the old one open lengthwise and see if anything seems different from a new barrel.

so basically, heat up, remove nozzle, and then spin through some of this Purging stuff?

Im likely not going to do that, just curious

You can try running virgin material first, no harm in that. What diameter are you seeing?

How much material have you extruded so far? All ABS?

http://www.ebay.com/itm/ASACLEAN-PURGIN … 4d207f158a

I'm fairly sure this is what the nozzle cleaning filament is made of. 

When I had this problem, only replacing the barrel seemed to work.  Maybe there is something that changes in the surface of the barrel that reduces the friction.  If you get a new barrel, it might be worth cutting the old one open lengthwise and see if anything seems different from a new barrel.

I have indeed verified that the barrel cut is relatively upright.  its a few degrees off of center, but I have tilted the hopper slightly to compensate (total movement at the tip of the hopper:  less than 1/2 of an inch).

It was a %*($% to put the enclosure together, so i would really rather not take it all apart...   

Would you think that running it to Natural, and then maybe Burning through a couple hoppers worth of material to Flush the colorant would help on its own?  or should I really be Gutting and Soaking?

http://www.soliforum.com/post/65178/#p65178

It is hard to narrow down the cause with so few folks experiencing the problem, and I've only experienced it once myself.

The other 6 customers saw extrusion drop even lower than you - less than 1"/min. If the barrel cutout is still facing up (and you are running horizontal, as vertical hoppers sometimes have feeding problems) then you may want to disassemble and soak the barrel in acetone to clean it. If that doesn't work, I can send out a replacement barrel/auger.

I would also check that the shaft collar has not slipped, the auger being out of the melt zone would cause this as well.

What colorants were you running?

Is the cutout in the barrel still facing completely upwards?

I have tried using some very-lightly mixed red (pink?) from OSPrinting  back when they were closing down --- extruded beautifully a month or so ago, but now not-so-good
and also some medium-mixed (bag said 1:36 to 1:90, so i went about 1:60) Green from Mandy over at 3dsupplysource.  (i have also tried to thin this down more just in case)

Both are labelled as ABS colorants.

Is the cutout in the barrel still facing completely upwards?