Last week I took my carbine out for a little trigger time. It's been about three years since I last fired it. I experienced numerous failures to eject properly, resulting in some stovepipe-type jams, and in most cases in which proper functioning occurred, the fired cases were landing close to my feet. I know it has nothing to do with the ammunition, as it occurred with both GI ammo and my reloads. I think the action is OK, and the gas tappet seems undamaged and moves back and forth freely. My best guess is that the ejector spring in the bolt may be too weak due to age. Any other possible reasons that anyone else can think of?

If the bolt was coming back with enough force, then its probably your ejector spring and or plunger. Breaking down the bolt is might sound easier than it is. I know they made a special tool for that purpose. Apparently early bolts where know to lose their parts, so they made some changes back in the day and now its very difficult to get them apart unless you have that tool or three hands.

Check to see if the nut that goes around the tappet is tight. The staking on mine was not the best and caused the nut to loosen causing erratic function.

Is your carbine a original GI contract or an aftermarket made? Some of the aftermarkets had timing problems with the bolt locking up.

Mine is a 1944 Inland with the usual post-WWII changes, and the tappet nut is tight and staked in place. The action functioning seems to be OK, but ejection is weak. I know the bolt is difficult to disassemble and I do not have a disasssembly tool.

check CMP and see if they have the tool or a bolt availiable for sale for your 1944 vintage carbine. Kyle

My first thoughts would be the ejector and it's coil spring in the bolt face.
Spring kinked, weak or otherwise compromised so as to take pressure off of the ejector plunger itself and cause weak ejection.
MAybe the ejector plunger itself somehow not sliding freely withing the boltface against the spring pressure.
Take the bolt out and press on the ejector plunger. See if the plunger moves freely in and back out and that there is constant spring pressure behind it. It should take a bit of pressure to hand seat a case into the face of the bolt against the spring tension of the ejector.

Then the extractor w/ it's small plunger and coil spring. A worn extractor or even a small shaving from a brass case under there can sometimes allow the extracted case to drop off the bolt face a little and the ejector to kick it free but not free of the rifle,,stovepipe and sideways emptys lying in the action.
The little coil spring behind the extractor & plunger gets dirty and gummed up easily too making for poor extraction.
Try the extractor for constant spring tension and smooth movement..

Clean out the bolt and especially those two small parts. Replace the parts/springs if necessary. They are deffinetly problems in the M1 Carbine.
You don't really need the disassembly tool to do this, but they do make this a little easier I'm told. I've never used one personally.

Another thought is the gas port in the bbl. It can sometimes become plugged or partially obstructed. Not enough gas gets to the piston, not enough energy to the slide and bolt = weak ejection (and usually feeding as well,,but you didn't mention that)

You have to remove the piston and nut then take a very fine twist drill that will just enter the gas port up in the bbl and carefully poke it through there to clear it. No attempt made to enlarge it,,just clear it.

Just some thoughts.

The tool is available at various places such as Numrich, Sarco and others. Anyone who owns a carbine really should have one and learn how to use it. A good bolt tear down and cleaning every now and then is a good idea to keep a carbine running right and without the tool it is NOT easy. A weak ejector spring or old hardened grease can certainly contribute to the kind of problem you're having (and I've found more than one spring packed with old grease when tearing down military carbines).

I spoke to one of the gun parts guys at the local gun show this morning. He felt the problem involved either the extractor or the ejector spring. He had a number of carbine bolt parts. A replacement extractor is $40 (new GI) and an ejector spring is $5. Wow. He said the bolt can be disassembled and re-assembled without the tool but it helps to have two people. He had the tool and said that if I bought the parts he would install them. I may do that next month.

I don't believe there is any problem with the gas port being plugged.

How many different magazines did you use?

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I have something like 20 magazines, from 5 rounds to 30 rounds, mostly 15 rounds, but in this case I was using two different 5-round magazines with equivalent performance results.

Okay, just checking. Often times it's the simplest things that cause issues with M1 carbines and 30 round magazines are often the worst trouble makers for the problem you describe.

Otherwise, sounds like you're on the right track to me.

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Most likely the ejector itself. It could be spring related. Take a pin punch and push in on the ejector to see if it is moving freely. Sometimes a sliver of brass or some other such thing gets forced in there with the ejector and effects operation. You'll also be able to determine if there is enough tension on the spring. Sounds like disassembly and thorough cleaning of the bolt is in order.