Just taking a stab at it I would say that the extractor needs adjustment or the slide needs to be taken totally down and cleaned where the extractor inserts into the slide. I’ve had carbon and unburnt powder collect there preventing proper tension before. Why would it extract one and not the other besides being steel casing but not stuck. Perhaps diameter of rim on steel case out of spec. My two cents.
^^^^This is most likely^^^^
After you
clean out the extractor channel, inspect the extractor hook to make sure it is not broken or chipped. If it is good, reassemble the extractor and firing pin stop and check extractor tension with a fired case: with the slide off the frame, slip the case rim under the extractor hook and into firing position against the breech face. It should stay in place-- and should stay in place when shaken slightly. I also like to do this check with a loaded round. If the extractor will allow it to easily slide in place and it will not fall out with a slight shake, the extractor tension is pretty good.
Note: the round should slip up under the extractor hook smoothly. If it does not, the hook probably needs tuning.
Look here:
For extractor tension adjustment, look here:
If tension is good, and the hook is good, check the fit of the firing pin stop to the extractor groove. If the stop is too loose (likely) or the groove is cut too large (unlikely), the extractor may be loose enough to move a bit forward and back in the channel, changing extractor effectiveness. You will need to fit an oversized firing pin stop to correct that problem. (Easily done). If the firing pin stop is too loose (thin) and too narrow across the rear of the slide, the extractor can also rotate slightly in the channel. (Also corrected by fitting a new oversize FPS)
All of this to say: If the extractor is in good condition, tensioned properly, and the channel is clean, a properly fitted extractor/firing pin stop should keep the extractor from moving in its channel, both rotationally, and forward/backward. The key to getting good and consistent extraction is "all of the above" and cartridge cases that are in spec.
I've had 2 RIA's and both had rather loose factory firing pin stops. Not enough to be a consistent problem of any sort, but both guns became more reliable with new FPS's.
I strongly suspect that a new firing pin stop is in your future! (however, a good cleaning could be just the ticket!)
