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Discussion Starter #1
Hi everyone!

Just got my first HK a few days ago, one of the P30 handguns from CDNN they are advertising. After shooting it at the range for a while this morning, I noticed when policing my brass that there's a tiny bulge in the cases ejected by the HK. I don't see this with my glocks or M&Ps. Is this normal based on chamber tolerances in the HK design? Does it cause a problem reloading? (I've been collecting all my 9mm brass for 6 months, but haven't started reloading yet)

The ammo was brass-cased FMJ Federal American Eagle, 115gr, normal pressure, recent manufacture. I did break in the gun with 124gr +P as was recommended, though it has never hiccuped (unlike my Gen4 glocks which were all bit by the various parts issues)

If this sounds completely abnormal, I can take a picture and upload it, but if this is common I won't bother. The bulge is a fraction of a millimeter I would guess, can't really feel it but can see it in the light.

Thanks!
--gos
 

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There is a step in the chamber. Nothing to worry about. The step is visible when you have the barrel out of the gun.
 

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Discussion Starter #3
Thanks! Now that I'm looking for it specifically, the step in the chamber is obvious.

P30 chamber:


P30 brass on the left, G17 brass on the right:


Appreciate the quick answer!
 

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You're welcome, and welcome to the forum. I only charge all of your brass with the step in it. Enjoy your pistol.
 

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I would hope your Glock has that same chamber step because that is what a 9mm chamber is supposed to have!
 

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I think the step is piece of the the HK accuracy secret. A nice alignment of bullet to bore, without compromising feed reliability.
 

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I think the step is piece of the the HK accuracy secret. A nice alignment of bullet to bore, without compromising feed reliability.
A stepped 9mm chamber provides a better gas seal between the casemouth and the chamber walls. The 9mm Luger is a tapered cartridge. . . meaning it is widest at the base of the cartridge and gradually tapers as you go toward the casemouth. If you stop and look at it carefully, you'll see it. Often, more expensive 9mm pistols (think German) have stepped chambers. The 9mm pistol chambers you see today in many pistols like CZ and others are not stepped but merely tapered. It is less work and less expensive to produce a tapered chamber for 9mm pistols than it is to produce a stepped chamber.

I believe the original designs for the original P-08 designed by Georg Luger in 1904 had the stepped chamber as in this very old drawing:

 

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It's an HK exclusive feature, the round was never designed to have it. Both of my P2Ks have the same thing.
 

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A stepped 9mm chamber provides a better gas seal between the casemouth and the chamber walls. The 9mm Luger is a tapered cartridge. . . meaning it is widest at the base of the cartridge and gradually tapers as you go toward the casemouth. If you stop and look at it carefully, you'll see it. Often, more expensive 9mm pistols (think German) have stepped chambers. The 9mm pistol chambers you see today in many pistols like CZ and others are not stepped but merely tapered. It is less work and less expensive to produce a tapered chamber for 9mm pistols than it is to produce a stepped chamber.

I believe the original designs for the original P-08 designed by Georg Luger in 1904 had the stepped chamber as in this very old drawing:

I love this place. In 42 years I've never seen a stepped 9mm chamber anywhere other than modern HK firearms. Then today, while I'm typing my comments, someone comes up with an old drawing of a stepped chamber. Learn something new every day.
 

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I love this place. In 42 years I've never seen a stepped 9mm chamber anywhere other than modern HK firearms. Then today, while I'm typing my comments, someone comes up with an old drawing of a stepped chamber. Learn something new every day.
Ha ha ha, I believe that many Walther pistols also have a stepped chamber!
 

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So then if you took an hk with a stepped chamber with a barrel length of 4.0 inches and another firearm with a tapered chamber with a 4.0 in barrel, and shot the exact same ammo, wouldnt you end up with higher velocities (or more consistent)out of the stepped chamber?
 

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So then if you took an hk with a stepped chamber with a barrel length of 4.0 inches and another firearm with a tapered chamber with a 4.0 in barrel, and shot the exact same ammo, wouldnt you end up with higher velocities (or more consistent)out of the stepped chamber?
Yes, the velocities should be more consistant and slightly higher out of a stepped 9mm chamber. . . and less powder-streaking on the outside of the case.
 

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Same reasoning behind the polygonal rifling. Smoother surface creates a better gas seal behind the bullet. IIRC tests by HK Germany saw a 3-6 percent increase in velocity vs conventional land and groove. Problem is, its expensive and slow to manufacture. So they only use it now on the pistols. Older G3's, 41 and 43's had the poly rifling.
 

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Neat, didn't know that.
 
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