I have an AR22 - an AR15 lower with a 22LR upper.  I've been using it for Steel Challenge for a few years.

Earlier this week the gun wouldn't eject the rounds properly.  I've manually cycled snap caps, and the round is being extracted, but not ejected.  It just kind of falls off the bolt face and dies inside the action.

Any suggestions as to what might be going on?

Sounds as if your ejector broke.

Is there crud under the extractor ?

Crud keeping the ejector from moving properly or on the bolt face as above said. Could also be a broken or just worn out extractor spring... sounds to me like the rd is falling off the bolt before it even contacts the ejector.

Thanks, I’ll check that.

No, I disassembled and cleaned the whole bolt.

Methinks this as well.

You didn’t mention which brand of 22 upper.  If you drop the hammer on an empty chamber on the 22 rimfire barrel you can peen the rear face of the barrel which can lead to feed and extraction issue.   Brownell’s sell a tool to remedy a battered rimfire barrel.  If I get sticky extraction in a rimfire barrel I polish the chamber with Flitz on a barrel mop attached to a short cleaning rod spun by a hand drill.

It is possible you have a worn extractor or extractor spring but most 22 conversion bolts have a fixed ejector.   On the Atchisson designed CMMG/Ciener/Velocity/Spike bolt the ejector is on the guide rail.   Nordic’s ejector is attached to the barrel and does not come out with the bolt when cleaning.

There's no ejector in the AR22 bolt face ;)

Clean up the extractor area, inspect it for chips and replace the spring with a heavier one and you'll be ready to rock again.

On the CMMG pattern, can't the ejector snap off the frame?  It seems so thin.

Anything is possible but  I’ve never seen it happen.  I’ve read where the ejector got bent or deformed but the bolt still has to slide on the rails which limits how much the ejector can be out of alignment.   If the bolt extracts live rounds out of the chamber the extractor is probably gtg.   I’m betting the chamber is rough or peened enough to inhibit extraction.   If you dry fire a 22 rimfire the barrel can be damaged pretty quick.   I ruined a DPMS Gen 1 barrel with ten round mags.  Repeated firing pin hits on the barrel from the firing pin eroded the end of the barrel plus it was hard on the firing pins.   No bolt hold open follower sucked on the DPMS ten round mags.  

If the extractor will not extract live rounds at all it might be a bad extractor or the extractor is not fitting in the groove on the side of the barrel when the bolt is in battery.

OP never mentioned the brand of upper so could be Chiappa,  Tactical Solutions, TACCOM/Velocity, Spikes, Model 1, Nordic/JP/RRA/DPMS G-2 or even a CLE.

On a blow back 22 rimfire the primary extraction is from the force of the igniting cartridge being pushed back by the chamber pressure.  I’ve seen 22 semi auto rimfire guns function with no extractor.    The extractor is important in controlling the cartridge during feeding and for unloading.   A worn or poor fitting extractor can still be the problem especially if the gun has been fired a lot.

What brand?

I had issues with a brand new cmmg. First they sent my a new extractor and spring but that didn't fix it. I ended up getting a new set of stronger springs from a guy on arfcom who's been producing a bunch of 22lr accessories - https://borebuddy.com/product/22lr-power-extractor-springs/

The 200% spring cleared my issues up, gun has run great ever since.

It's a Tactical Solutions 22lr upper, about 3 years old.

I cleaned the bolt and barrel as well as I could.  Now, I'll head to the range to see what happens.  Also, I'm bringing a CMMG 22lr upper with me to make sure that one runs too.

Oh, and I ordered the stronger extraction springs from Bore Buddy.  Good company, good products.  I'd already gotten their buffer weights for the CMMG bolts, and they work great.

I also have the D-fender extractor upgrade for AR-15s that I'm going to try to see if they fit the 22lr bolts.

It will be interesting to see if Tactical Solutions offers you any assistance.  There has been speculation that since they no longer sell AR22s, that they will not service them.  Have you tried reaching out to them for a replacement extractor or any service for matter?

Bottom line: my expectations of proper ejection with hand-cycling was unrealistic.  It seems that yes, you really need to shoot the rounds to have enough force to eject them out of the upper.  Of course, [ahem] cleaning the BCG does seem to help a bit there also.  I stripped it down and cleaned  everything I could.

Also made one change to the BCG.  I used (part of) one of these:

https://www.brownells.com/rifle-parts/bolt-parts/extractor-parts/extractor-hardware/ar-15-extractor-spring-upgrade-kit-prod133591.aspx

It consists of a new spring, an O-ring, and a plastic insert for a regular AR-15.  For the 22LR only the black insert fit into my bolt, inside the extractor spring.  Whether that actually made a difference or not I don't know, but I'm leaving it in.

Took the gun to the range, and it ran perfectly.

Thanks for everybody's feedback.