Damaged 10mm Brass [Archive] - Glock Talk


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11-13-2011, 06:42
I recently picked up a KKM 10mm conversion barrel for my Glock 21sf. I added a 22# spring and steel guide rod.

The other day I went out to the range with some reloads I made up with some new Top Brass cases. I use a 180 gr zero bullet with 8.2 gr of Power Pistol.

The first 20 or so rounds seemed to be ok. Then I started having FTF malfunctions. It was closing time for the range so I just packed up and went home.

Then next day when I looked at my spent brass i saw the damaged cases you see below. Looks like they are getting mangled by the slide as they eject which probably caused the malfunction.

Any ideas what is causing this and how to fix. I've read that it could be the length of the ejector. Do I need to get a G20 sf ejector to make this work?

KKM said it should work with just the extractor mod.

Thanks for any advice you can give.



11-13-2011, 06:51
Obtain a factory Glock G20 guide rod & spring assy.

11-13-2011, 07:37
I looked on Glockparts and they sell the same spring assembly for the G20 and G21. Is there a heavier Glock 20 spring assembly? Do I need the heavier spring?


11-13-2011, 07:51
No,....you could try the factory G21 spring assy. I do not think you
need a heavier spring assy. I thing the 22# spring may be the problem.

Are you using a G20 trigger housing with the conversion barrel?

11-13-2011, 07:56
I'm using the G21 housing. I'll try the STD spring this morning

11-13-2011, 09:29
Standard spring was 100%. No casualties. I guess the 22# spring is for full power loads. It was a long walk to retrieve the brass but indoors it doesn't matter


11-13-2011, 09:46
I did exactly the same thing a few years ago. I had problems with jams and mangled brass. I was never able to totally eliminate the problem. It jammed 10% of the time at least. Best solution to this problem is to buy a dedicated 10mm pistol. I bought a Kimber 1911, but many like the Glock 20. Problem solved and lesson learned.

11-13-2011, 10:43
The problem as I see it...what I am speculating is that the extractor is pinching too tight and still holding the casing in contact with the breech even as the next cartridge is trying to slide up in position, with the slide moving forward toward battery of the next round the casing which was to be ejected is being slammed into the top or side of the barrel. Try and test this pinching affect by slideing an empty casing up under the extractor and feel if it was different for the two different cartridge cases...I suspect he would feel where the 10mm case is being held tighter under the extractor than the 45ACP due to the difference in extraction rim thickness...

10mm rim is 0.0550" / 1.40mm
45ACP rimis 0.0490" / 1.24mm

Difference is 0.0060" / 0.16mm I feel this difference is the issue he is experienceing...http://thefiringline.com/forums/images/smilies/confused.gif

The 45ACP case is 0.4800" / 12.90mm in dia. and 0.8980" / 22.81mm long

The 10mm case is 0.4250" / 10.80mm in dia. and 0.9920" / 25.20mm long

Case length difference is only 0.094". Both are usually loaded to the same physical length of 1.26" for the 10mm and 1.275" for the 45ACP therefore the length of the cartridge is not and issue...

The physical dia. difference 0.055" /2.10mm and could be missing the ejector at times. This could be distance might actually increase if the extractor is holding the casing tightly and the forward edge of the case angles to the right, that shift slightly toward the right could increase the distance at its case head.

I still lean toward the extractor holding 10mm cases too tightly against the breech face to let it be knocked off and out from under the extractor. The ejector may only move the casing over to the rightside instead of kicking it out from under the extractor! This can also hamper the feeding of a fresh cartridge trying to pop up and slide up the breechface and into battery.

Here is where we were discussing this very same situation a fellow in Sweden was using the 10mm conversion barrel also...The Firing Line forum
http://thefiringline.com/forums/showthread.php?t=468287<!-- / message --><!-- BEGIN TEMPLATE: ad_showthread_firstpost_sig --><!-- END TEMPLATE: ad_showthread_firstpost_sig --><!-- sig -->

No Mercy
11-13-2011, 13:04
My G29sf was doing the same thing. I had KKM barrel and wolf 21lb. spring assy. It crushed brass just like that,even worse at times. Never failed to feed or eject though. I switched to the 19lb. wolf spring and it solved most of the problem. That heavy spring is slamming the next round and slide forward with alot more speed and I believe the fired case is getting slammed into the barrel hood on ejection. Mine only did it with really hot loads. Went to the range yesterday and the little G29 was 100% reliable with everything I ran through it. :)
I was running 180gr Gold Dots loaded with 9.7gr. of Power Pistol with no problems,but the recoil was a....rather stout! And that load has the biggest damn white flash out the muzzle!! Lite up the whole indoor range! Several people stopped shooting and come over to see what kinda Gun I shooting. LOL! They were surprised to see such a small gun making so much noise. ;)

11-13-2011, 13:41
I've had the same thing happen with my LW 6" bbl.