Betcha didnt know that 9mm Luger pistol chambers are

heckinohio · Apr 24, 2018

stepped.????? I have copies of the original chamber drawings for the 9mm cartridge.....and looking into the chamber at a rather steep angle, one can clearly see the step...

However, several older established barrel reliners deny such a stepped chamber exists. Apparently they dont happen to have an un-relined example to look at, and who wants to admit that he has done it incorrectly for the past 40 years..???

I have the drawings, who can I get to make the chamber reamer..??? Drawings are in the original metric dimensions. I havnt explored the possibility of a .357/38 reamer being reground...dont know how the case body ODs compare.

PJH

thermite · Apr 24, 2018

heckinohio said:
stepped.????? I have copies of the original chamber drawings for the 9mm cartridge.....and looking into the chamber at a rather steep angle, one can clearly see the step...

However, several older established barrel reliners deny such a stepped chamber exists. Apparently they dont happen to have an un-relined example to look at, and who wants to admit that he has done it incorrectly for the past 40 years..???

I have the drawings, who can I get to make the chamber reamer..??? Drawings are in the original metric dimensions. I havnt explored the possibility of a .357/38 reamer being reground...dont know how the case body ODs compare.

PJH

I did not know that. I have long been aware of OTHER firearms wherein a departure from pure cylinder made use of case obturation to retard blowback. But the Luger's "toggle" action is not a pure blowback, and "modern" usage doesn't really count, does it?

Let's see what ripples arise from this pebble flicked into the still and ancient pond...

Well over a hundred years BTW. Not just 40.

Not sure "40" even covers the variety of chamberings for things 9 mm-ish.

Street · Apr 24, 2018

Try pacific tool and gauge here

Chamber Reamers, Headspace Gauges, and Firearm Accessories Since 1957 - Pacific Tool and Gauge

For a quote to make

GunBum · Apr 24, 2018

Could you post the original drawings?

Danny VanVoorn · Apr 24, 2018

No gun smith here but it seems all semi auto/auto ammo requires some step somewhere in the bore, the rim certainly doesn't stop it from moving too far forward?
Dan

JLarsson · Apr 24, 2018

"Stepped" is probably nothing more than the transition between chamber and throat. In theory, this is where headspace is established when the case mouth comes to rest against it. In actuality, depending on the firearm (and I don't know about Lugers), the extractor often holds the rim of the case against the breechface, meaning the case may or may not actually headspace in the proper manner.

thermite · Apr 24, 2018

JLarsson said:
"Stepped" is probably nothing more than the transition between chamber and throat. In theory, this is where headspace is established when the case mouth comes to rest against it. In actuality, depending on the firearm (and I don't know about Lugers), the extractor often holds the rim of the case against the breechface, meaning the case may or may not actually headspace in the proper manner.

LOL! "Much ado about nothing" perhaps? Dunno much about P'08's, either.

But for-sure there have been whole clans and tribes of pure blowback eaters-of-Parabellum as do not even OWN an "extractor" and find that headspacing on the case mouth edge does improve firing-pin facsimile teat reliability!

MilGunsmith · Apr 25, 2018

Can you make a chamber cast and post the picture? Then we can all see what we are discussing.

michiganbuck · Apr 25, 2018

I knew a fellow who brought back a Luger and deliberately let it rust to scrap..He was the only one of his squad who lived and the gun going scrap was getting even.. Yes now he is past and I have no idea where that gun went. Just saw his wife and his son last year but did not ask about the Luger.

9mm luger bore reamer dimensions - Google Search

tkingmo · Apr 25, 2018

heckinohio said:
stepped.????? I have copies of the original chamber drawings for the 9mm cartridge.....and looking into the chamber at a rather steep angle, one can clearly see the step...

However, several older established barrel reliners deny such a stepped chamber exists. Apparently they dont happen to have an un-relined example to look at, and who wants to admit that he has done it incorrectly for the past 40 years..???

I have the drawings, who can I get to make the chamber reamer..??? Drawings are in the original metric dimensions. I havnt explored the possibility of a .357/38 reamer being reground...dont know how the case body ODs compare.

PJH

yes, because it headspaces on the case mouth.

DanielG · Apr 25, 2018

Here's the chamber cross section according to the drawings I have.

DanielG · Apr 25, 2018

Also, it appears to be not just stepped, but the second step has a shallow taper to it, from 9.75 at the breech end to 9.70 at the muzzle end.

This is getting a little bit away from the stepped chamber, but the thing I've always wondered about on the P08 barrels is how they clocked them consistently. If you're building one you would hand fit the barrel and receiver so that they were properly aligned. How did they do it in mass production back in the day? These days with CNC, the problem is much easier, but that wasn't really an option back then.

steve-l · Apr 25, 2018

heckinohio said:
stepped.????? I have copies of the original chamber drawings for the 9mm cartridge.....and looking into the chamber at a rather steep angle, one can clearly see the step...

However, several older established barrel reliners deny such a stepped chamber exists. Apparently they dont happen to have an un-relined example to look at, and who wants to admit that he has done it incorrectly for the past 40 years..???

I have the drawings, who can I get to make the chamber reamer..??? Drawings are in the original metric dimensions. I havnt explored the possibility of a .357/38 reamer being reground...dont know how the case body ODs compare.

PJH

They are NOT stepped. What you are referring to is a lip that the case mouth butts up against when chambered. This lip is required on all un-shouldered auto cases because there is no case rim to register against. This makes case length important if you are reloading.

DanielG · Apr 25, 2018

steve-l said:
They are NOT stepped. What you are referring to is a lip that the case mouth butts up against when chambered. This lip is required on all un-shouldered auto cases because there is no case rim to register against. This makes case length important if you are reloading.

The lip that the case mouth butts up against is the one at 17.1mm in, where the diameter goes from 9.7 to 9.08. I'm pretty sure Heckinohio is referring to the very minor step at 12.1mm in, where the diameter goes from 9.85 to 9.75.

Scottl · Apr 25, 2018

DanielG said:
Also, it appears to be not just stepped, but the second step has a shallow taper to it, from 9.75 at the breech end to 9.70 at the muzzle end.

This is getting a little bit away from the stepped chamber, but the thing I've always wondered about on the P08 barrels is how they clocked them consistently. If you're building one you would hand fit the barrel and receiver so that they were properly aligned. How did they do it in mass production back in the day? These days with CNC, the problem is much easier, but that wasn't really an option back then.

I'm pretty sure mass production back in the day still involved some hand fitting. Perhaps the parts were fitted to master gauges prior to actual assembly. That would also make repairs at depots easier since a replacement barrel should fit without machine work.

My suspicion is that they either hand fitted them to the gauges or more likely sorted both barrels and receivers according to which gauge they fit and matched them at assembly using some sort of code.

thermite · Apr 25, 2018

Scottl said:
I'm pretty sure mass production back in the day still involved some hand fitting. Perhaps the parts were fitted to master gauges prior to actual assembly. That would also make repairs at depots easier since a replacement barrel should fit without machine work.

My suspicion is that they either hand fitted them to the gauges or more likely sorted both barrels and receivers according to which gauge they fit and matched them at assembly using some sort of code.

Not an accident. Done a-purpose. The P 08 was intended to be an armed forces and police sidearm.

The relief, arse end, helped reduce sensitivity to chambering even undetectably damaged or slightly imperfectly made cases.

The tighter diameter forward tried to preserve accuracy.

A forcing or guiding cone before the projectile tip engaged the rifling and got itself "engraved" helped get it off to a straight start, yet allowed clearing the weapon many times without damage to the round - preserving re-use being a necessity.

Consistency of production of ammunition generally improved, 1908 or so onward. Not all of these "tricks" would have remained of equal value to all makers, all designs.

Most of which were inherently BETTER ones anyway, FWIW.

Not a lot of "design wins" that action, very long time now. It wasn't even Standard "A" for WWII Germany. Substitute, rather.

RWO · Apr 25, 2018

The official SAMMI spec is here: http://www.saami.org/specifications_and_information/publications/download/205.pdf (page 26)

thermite · Apr 25, 2018

RWO said:
The official SAMMI spec is here: http://www.saami.org/specifications_and_information/publications/download/205.pdf (page 26)

No help. That's an ammunition spec.

Must be a thousand firearm designs as have been chambered for the cartridge by this late date.

Locked breech, unlocked breech, retarded blowback.. uber precise for the range, well-clearanced for mud, blood, and sand..Artic winters.. rapid clearing of water for UDT / SEAL type swimmers, different nations needs .. all sorts of approaches ..

Pretty well certain a WW II STEN didn't have the same chamber profile as Luger's P'08, if only because it was allegedly designed able to also fire .38 SPL ammo (rimmed) if need be - same STEN, not with an adapter, either. Then there will be ramp cutouts, most slide-operated semi-autos.

Add fluted chambers for delayed blowback (a CETME trick to tame rounds as were too hot for unretarded blowback).

I'd not go so far as to say no two designs ever used the same exact same chamber specs, - reamer sales say otherwise. But there surely have been a fair share of "departures from the norm".

excello · Apr 25, 2018

I have a set of books with nothing but chamber and cartridge dimensions. Here's what is shown for 9mm Parabellum. Not saying it is correct - just adding info (or dung ?! ) to the heap.

excello

thermite · Apr 25, 2018

excello said:
I have a set of books with nothing but chamber and cartridge dimensions. Here's what is shown for 9mm Parabellum. Not saying it is correct - just adding info (or dung ?! ) to the heap.

excello

None of the standards are "wrong".

But yah have to figure that G. Luger & his team needed to mess about a little to insure they had the ability to pass acceptance tests for function as well as accuracy. Early-on, I'd surmise Borchardt was still a competitor for the same contracts.

The Swiss were early-adopters, and they were picky folks at the time as to stuff having to JFW. Not that you'd know it from first-gen SIG-Neuhausen semi-autos, but...different generations.

The step the OP reports may have given Luger a reliability edge as to feeding and extraction.

I was not in the room, BTW. Just usta read a lot.. and back when these goods were more than half a century younger and ....published info .. BS, anecdotal / urban legend or .. "real" was still fresher than it is now.

Betcha didnt know that 9mm Luger pistol chambers are

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