The Minority Marksman.
"When you meet a swordsman, draw your sword: Do not recite poetry to one who is not a poet."
-a Ch'an Buddhist axiom.
YES.
Getest thee to thy local WalMart automotive section, and pickest thee up a can of NON-CHLORINATED brake cleaner.
Solvent with some ass behind it. Dissolves AND flushes. Blasts into all kinds of nooks/crannies, like striker channels and, say, external extractors. Evaporates fast, doesn't leave behind much of anything, and what it does leave behind can be wiped off. If you don't wipe that off, it still doesn't harm rubber, plastics, metal finishes.
Stuff with chlorine can harm, so look for "non-chlorinated" or "chlorine-free" on the label.
Works on the carbon that gets BAKED onto the components of an M240 without damaging the gun; that stuff's harder than Chinese differential calculus, scraping it was like chipping the edge of a piece of flint to make a Folsom spearpoint. Brake cleaner = trade scrapers for blue paper shop towels.
The stuff found under a pistol extractor is laughable, by comparison.
Quick update. Problem solved. I found a big buildup of crud on the breech face under the claw and cleaned it off. 150 trouble free rounds so far (I don't as much as I should) and nary a problem. My accuracy at 25 yards on the other hand....
This is essentially what I started doing also after my first experience seeing the carbon build up on a 92 and PX4 extractor. Every 3-4 cleaning cycles I blast/flush out the extractor area with breakfree powderblast.
I go through the external extractor area and then through the firing pin area. Then I blow it out with compressed air.
I've done this for years and have had no issues.