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Broken Extractor


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#1 85th Engineer

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Posted 02 November 2004 - 01:37 PM

Took my Kahr 27 out to the range today to kill time while waiting on election returns. I fired some 20 rounds and the extractor broke. Not long ago it was re-chambered and headspace adjusted. After that I noticed there was a lot of carbon blow by on one side of the case and there is a slight bulge that encircles the case which is more pronounced on one side (enough to feel and see). I got out some pre chamber work cases that I'd fired last year and cannot see a bulge or any carbon blow by. In addition, the case that was left in the chamber when the extractor broke has a much deeper and wider pocket in the primer than is normally left by the firing pin. Does that mean something, or is that where the firing pin struck it a second time when I tried to fire the gun again after the extractor broke?

I'm not all that familiar with the direct blow back action to know what should be going on. Have I got a bad chamber problem now, and am I just wasting my time if I buy another extractor? Are these markings on the spent cases acceptable, or do I now have a problem that is just gonna keep breaking extractors?

Also, when I do replace the extractor, are the Kahr semi-auto extractors interchangable with the originals? Where should I order another extractor? Do I go back to Kahr, or is there a better source?

Thanks in advance for your answers.
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#2 TommyGunner

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Posted 02 November 2004 - 01:54 PM

Just a question...

Were you using the same ammo before and after the chamber work? Factory loads? I have seen folks try a load that is way hotter than a guns spec. (on other guns as well) This causes the case to expand to much in the delayed blowback and the empy case can get jammed in the chamber. I have seen cases ripped in half with the tip still in the chamber requiring a broken shell extractor...sometime the extractor just brakes. If you have blowby...I suspect a chamber problem. IF there is a dimple on the side of the chamber, the expansion of the case into it could possibly cause the case to jam in putting extra stress on the extractor when you try to pull the bolt back. That could explain your buldge. The firing pin striking a second time could be the cause of the larger dimple on the primer. Can't tell without inspection of course but just a hunch. You could use a GI extractor. I would like to see a casting of the chamber to rule that in or out.

Good luck,
Damon
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#3 85th Engineer

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Posted 02 November 2004 - 02:12 PM

Thanks Damon. I was using the same ammo, Win. white box. That's all I've ever used. I don't think the bulge is excessive, but there is quite a bit of blowby on one side. Maybe I just had a bad extractor.

Now, how do I remove the broken extractor? Do you pry it up from the front end and push it forward from the rear? That's my best guess just eyeballing it.
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#4 PK.

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Posted 02 November 2004 - 03:53 PM

I would suspect that when your chamber was re-cut is was done to the GI chamber spec, which is a bit bigger than the pistol spec used by WH and Kahr in the semi barrels (which were often undersize, even for the pistol spec). The 45 acp is a relatively low pressure round and the chamber diameters were increased to maximize feeding and extracting reliability. Some low pressure gas will escape rearward and blacken the case slightly (usually on only one side); this is normal and will not affect the function of the gun or longevity of the parts, all blow back guns do it to some degree or other, especially with low pressure cartridges.

All of the extractors I have seen in Kahr guns are GI surplus- I have no reason to believe they are making their own at this time.

The semi guns seem to be harder on extractors than the FA guns. I believe the primary reason is related to the bolt mass problem (that requires the use of the heavy springs). Because the bolt mass is lighter than is should be, the gun opens faster, while the chamber pressure is higher. The bolt getting is first push while the pressure is low and then the case expanding into the chamber wall and gripping as the pressure peaks- the bolt continuing to move and the extractor trying to pull the restrained case. With a heavier bolt it all happens more slowly, giving time for the pressure to drop a bit before the extractor has to pull on the case.

In the other direction, the semi bolt is moving much faster than a FA one as the extractor engages and snaps over the rim. It’s all a bit more violent than the extractors were originally designed to handle- however they perform admirably well.

Any extractor of similar deign (80+ year old technology) is subject to breakage- that’s why they were a regular part in the spares kit, even for the FA guns. One that is a bit harder is more likely to snap than one that is a bit softer, etc.

The occasional broken extractor is no reason for concern to the Thompson owner.



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#5 85th Engineer

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Posted 02 November 2004 - 04:12 PM

Thanks PK,

Now how do I remove the broken extractor. It broke flush at the front edge of what appears to be where the extractor recesses into a hole in the side of the bolt. I'm assuming you have to pry up on the front (muzzle end) of the extractor to lift it out of the recess hole and push it forward out of it's grooved slot. Is that correct? If so, how do I get leverage to lift when there is nothing apparent to get under to provide lifting leverage? Am I gonna have to try to drill a small hole in the broken end to get a recess to lift?
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#6 PK.

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Posted 02 November 2004 - 06:22 PM

I’m sorry, you did ask that question and I failed to respond.

Yes, you have it right in every way. Sometimes the break will leave a positive shelf that you can use for lifting, otherwise you may need to create one. The extractor is hard- I use a small ball shape carbide burr to form a cavity in the broken end to allow use of a pointed lifting tool.

Before you go to that trouble, try a toothbrush handle- push back firmly on the broken extractor while prying. The brake may be rough enough to provide adequate purchase in the relatively soft plastic.

All this is easier to do if the bolt is supported in a bench vise. I don’t know how they did it in the field.

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#7 TommyGunner

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Posted 02 November 2004 - 06:51 PM

PK,

Excellent info! What would cause the buldge in the side of the case in that instance?

Damon

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#8 85th Engineer

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Posted 03 November 2004 - 02:34 AM

Thanks for all the help fellas. Looks like I've got a tough test of my patience ahead of me tomorrow dealing with this extractor. About as tough of a test as it's gonna be waiting on John Kerry to toss in the towel.
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