Just for the hell of it and certainly before doing anything else to the pistol, I'd use a completely different lot of ammo of the same brand and configuration you always had success with. I know some M41's are very finicky as to what you feed them. My personal version runs 100% with CCI 40 grain Std. Vel. ammo however even CCI can have a lot that varies once in awhile. I had one brick of CCI (at the height of the ammo crises) that contained more "duds" due to badly primed cases than all the CCI ammo I have ever shot!! Hey, it happens - worth a try.

I'd also check the Chamber, Extractor, Slide Face, etc for any peening, burrs, or anything out of the ordinary. Use a magnifoer and a bright light to inspect. I've seen a recoil spring change to a 1/2 pound lighter version work sometimes. Just make SURE you install the spring in the proper orientation IF you go with one of the Wolff after market springs with an opened coil on one side. The opened coil MUST face the rear of the pistol or it will jam the gun up in short order. If you do use one of these one side unfinished springs, mark it so you NEVER instal it the wrong way. NOTE: Factory springs have both sides finished. Wolff may have corrected this issue - I have not checked their new production.

It sounds like you have had this M41 for a while and so if it ran great for a long time, obviously something has suddenly changed. Do you know approximately how many rounds have been shot through the pistol? I'd also (just to be positive) install another Volquartsen Extractor. Maybe the one you did install is not to spec or has a slight malformation - leave nothing to chance. Once in a blue moon even the best manufacturers have a bad part. I have had bad parts some from top notch manufacturers - not very often but it has happened! For the inexpensive cost and 20 minute of your time it's worth a try.