Glock 20SF ejected brass. What causes this?

[goldenbear926]

I have been doing some load development in my Glock 20SF Gen 3 and have been getting some brass back with strange indentations on the case mouth. It has not caused any failures but perplexes me none the least. It seems to occur every five rounds or so. These indentions have happened with a 4.6" KKM barrel and a 6.0" Lone Wolf barrel. The gun has a Lone Wolf SS guide rod with a 22# spring  the gun is stock otherwise. The loads I am loading are high power Double Tap / Underwood power loads using 180-230 gr. bullets.

The indentations on the case mouth line up with edges on the chamber hood of the barrel. One side of the case mouth has a slightly wider indentation that the other. See photos.

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[The_Shadow]

Have you tried your stock factory spring to see if it still occurs?  The brass may not be kicked off the extractor for one of two reasons.
1. The slide may not be traveling far enough to the rear to be kick out and clear of the open ejection port or from under the extractor.  Slide may be delayed slightly by the case expansion holding too long in the tighter chambers or the recoil spring system may be bunching up while trying to run the full length of the slide travel to be kicked free and clear.
2. The extractor may be holding the casing too tight, inspect, check for roughness of the breech face and clean and lube extractor.

Maybe a combination of both...

[sqlbullet]

Almost certainlyvextractor related.  I have had the same issue in my 1911.  Not extractor tension fixed it for me.  I would detail strip the slide and clean it all good.  On reassembly check the tension with an empty case.

[BillC]

I had a few pieces of brass look like that shooting some Underwood using stock spring and barrel. I put in my 22lb spring and the problem disappeared.

[arttyszka]

Almost certainlyvextractor related.  I have had the same issue in my 1911.  Not extractor tension fixed it for me.  I would detail strip the slide and clean it all good.  On reassembly check the tension with an empty case.

Hi sqlbullet, I'm having a hard time understanding your post, I have this exact same issue with my Kimber SS Target II, I originally was told that the extractor was likely not holding the case tight enough so I tightened it, but that seems to have made it worse.  Did you fix this issue by lightening extractor tension in your 1911?

Thanks
Art