Luger Chambers VS Modern Chambers

[Doubs]

I reload for my handguns in both .30 Luger and 9mm Luger... or Parabellum, if you wish.

My favorite bullet for 9mm is a 115 grain plated Berry's flat base, flat nose bullet that is really a truncated cone close to the original German military design. You can see the bullet and how I load it for my Lugers on the far right of the picture below.

ALL of my original "Shooter" Lugers work beautifully with this cartridge as seen in the picture. Same with my original .30 Lugers and the cartridges as seen in the picture.

OTOH, modern guns chambered for these cartridges do not work well with these loads. The chambers and leads are cut differently and the bullets jam into the lands, preventing the actions from closing. The difference in seating depth is as much as .070" or 70 thousands of an inch. None of my newer 9mm handguns will accept my Luger loads because the bullet jams the lands.

Interestingly, a 1942 Mauser P-38 won't chamber my 9mm Luger load but a 1986 P1 does. My Sig P6, CZ-75B and Grand Power K100 pistols all have short leads that require seating the bullets deeper. My .30 Luger loads won't chamber in my Benelli B80 or Browning High Power; the bullet must be seated deeper in the case.

For anyone new to reloading, the manuals list an over all cartridge length and that may - or may not - work in your pistol depending upon the bullet design and your chamber. Remove your barrel, make up a dummy round and make sure your load will chamber without jamming the lands. If your bullet is seated deeper than the manual calls for, adjust your powder weight to prevent higher pressures.

[mrerick]

Note that the OAL listed for cartridges in reloading guides are for specific bullets (and bullet profiles).

You can't use the same OAL for a round nose bullet as you would for a flat nose one. It will result in the bullet being seated too shallowly in the case, and this can seriously change the ballistics at time of ignition, the jump into the leade and the engagement hesitation delay. This can then change the peak pressure(s) considerably from what was found experimentally in the manual.

Your 9mm Luger round looks seated far shallow into the case. The bullet should never be actually in contact with the leade while chambered. It needs the "jump" across an air gap to gain adequate acceleration prior to the resistance of leade engagement and hesitation as it starts traveling in the rifling.

What reloading manual are you using, and which cartridge / bullet / powder / primer combination?

[Doubs]

Originally Posted by mrerick

Your 9mm Luger round looks seated far shallow into the case. The bullet should never be actually in contact with the leade while chambered.

It doesn't touch the lands or leade in any of my shooter Lugers which is the whole point of my post. Loaded to an OAL of 1.100" as seen in the picture, there is still a jump to the lands. OTOH, my more modern pistols require seating much deeper for the same jump: 1.035" OAL. The original Luger chambers are much more generous than newer guns. The same applies to my shooter .30 Lugers. The chambers are more generous than newer pistols.

What reloading manual are you using, and which cartridge / bullet / powder / primer combination?

I have more than half a dozen manuals by the major companies; Lyman, Hodgdon, Speer, Sierra, Nosler, Hornady and a few others.

The closest in design to the Berry's plated flat base flat nose bullet is Speer's 115 grain Gold Dot. Hodgdon calls for a maximum load of 5.9 grains of CFE Pistol Powder and an OAL of 1.125". I use 5.6 grains and an OAL of 1.100" and my load drops fully into the chamber and drops freely out of it. Berry's bullets are plated and are softer than the jacket material of the Gold Dot bullets. The load functions my Lugers reliably, is accurate and shows absolutely no signs of pressure.

Cases are whatever I have and primers are standard small pistol primers by Winchester, CCI or S&B. I currently have some Genex that work well.

If you have a modern 9mm handgun, the chances are that the chamber is cut differently than a vintage Luger. I listed three examples of modern handguns I have that require the same bullet to be seated .070" deeper than for my Lugers or they will not chamber because the bullet jams the lands. For them, I lower the powder charge to Hodgdon's starting load of 5.4 grains of CFE Pistol Powder. Again, they give reliable function and accuracy without any pressure signs.

I've been loading for Lugers since 1966; both .30 caliber and 9mm. I've used just about every possible powder and bullet available. Some of the powders like Winchester 730 worked great but isn't made any longer. AA #7 leaves too many powder grains. Unique works beautifully but doesn't work well through a measure. Blue Dot and Herco work but are dirty. Bullseye and 231 are good powders and meter well. The list goes on but CFE Pistol Powder has become my go-to powder for a wide range of pistol cartridges.

[DonVoigt]

" It needs the "jump" across an air gap to gain adequate acceleration prior to the resistance of leade engagement and hesitation as it starts traveling in the rifling."

This is a strange theory, where did it come from?

[mrerick]

It's basic internal ballistics. Look up "freebore' and "throat". This is how the initial pressure peak is managed in a modern handgun or rifle chamber. For a reference, see George Nonte's classic book on "Pistolsmithing".

Consider this analogy... Driving a nail into wood is similar to pushing a bullet up the leade of a barrel into the rifling. When you drive a nail, do you put the mass of the hammer against the nail head and push, or do you swing the hammer's mass across a distance of air and strike the nail into the wood? You can still drive the nail without using the momentum and mass of the hammer, but it takes considerably more pressure building against the hammer before the nail will start to overcome the friction and start to move.

Without adequate freebore, the bullet won't have the momentum to easily engage the leade and start down the rifling. Pressure will continue building in the chamber until the movement finally provides more volume to expand in.

This can be measured in an instrumented chamber.

If a cartridge OAL is too long, the initial pressure peak will be higher and sometimes dangerous.

BTW, Luger was experimenting with the chamber of his design from the beginning. There is a step in his 9mm Chamber as well as an oblation ring to help with the seal and release of the case.

[Doubs]

Originally Posted by mrerick

BTW, Luger was experimenting with the chamber of his design from the beginning. There is a step in his 9mm Chamber as well as an oblation ring to help with the seal and release of the case.

Interestingly I have a Grand Power Stibog 9mm which is classified as a pistol by the BATFE. (It has a "brace" and not a shoulder stock) It's made in Slovakia and the action is a blow back design. The barrel is 8 inches and the magazines are either 20 or 30 rounds. Date of production is 2019. Accurate and reliable, it's the most fun gun to shoot that I own. (Picture below)

I use the same load in the Stribog as I do in my shooter Lugers. What's interesting is that the fired cases show that the chamber has a step in it. There is a clearly delineated line around the case where the step is smaller in diameter than the rest of the chamber.

Did the Grand Power engineers duplicate the original Luger chamber? The step indicates that it's possible.

WRT the bullet touching the leade or lands, in most cases it's a bad idea because of pressures. Some benchrest shooters and other precision rifle shooters will sometimes find their best accuracy with the bullet touching or even a few thousands into the lands. Their powder is adjusted to prevent high pressures. For those of us who shoot Lugers or other handguns chambered for .30 Luger or 9mm, the bullet should be a few thousands off of the lands. That was the reason I pointed out the differences in chambers between my vintage Lugers and newer production handguns.

[Chichaco98]

Walther PPS M2 also uses a stepped chamber.

[Sieger]

Gentlemen,

We have discussed the Luger's stepped chamber on this forum many times. The experts here have agreed that the design was originally intended to assist in gas sealing the 9mm chamber, due to the original powder available and used by D.W.M, at that time.

It is very interesting to me that newer designed firearms would copy such a design.

As noted above, original 9mm Luger military and civilian ammo was loaded out rather longly, as was their 8mm Mauser ammo as well.

Proper O.A.L. Luger ammo, as noted above, may be just too long to chamber in more modern designs, as round nose rounds can range between 1.169 and 1.173 inches.

As to maximum accuracy, in both rifle and pistol shooting, I have found that a bullet, just kissing the lands, to be the most accurate.


Respectfully,


Sieger

[Sieger]

Originally Posted by DonVoigt

" It needs the "jump" across an air gap to gain adequate acceleration prior to the resistance of leade engagement and hesitation as it starts traveling in the rifling."

This is a strange theory, where did it come from?

Don,

I agree with your comment fully!


Respectfully,


Sieger

[DonVoigt]

Originally Posted by mrerick

It's basic internal ballistics. Look up "freebore' and "throat". This is how the initial pressure peak is managed in a modern handgun or rifle chamber. For a reference, see George Nonte's classic book on "Pistolsmithing".

Consider this analogy... Driving a nail into wood is similar to pushing a bullet up the leade of a barrel into the rifling. When you drive a nail, do you put the mass of the hammer against the nail head and push, or do you swing the hammer's mass across a distance of air and strike the nail into the wood? You can still drive the nail without using the momentum and mass of the hammer, but it takes considerably more pressure building against the hammer before the nail will start to overcome the friction and start to move.

Without adequate freebore, the bullet won't have the momentum to easily engage the leade and start down the rifling. Pressure will continue building in the chamber until the movement finally provides more volume to expand in.

This can be measured in an instrumented chamber.

If a cartridge OAL is too long, the initial pressure peak will be higher and sometimes dangerous.

BTW, Luger was experimenting with the chamber of his design from the beginning. There is a step in his 9mm Chamber as well as an oblation ring to help with the seal and release of the case.

Sorry Marc,
I"m not buying the "jump" business- unless you can point us to an authoritative source- comparing a bullet to a nail is .
JMHO.

Benchrest shooters for years have set their bullets "out" to engage the rifling slightly just so the bullet won't "jump" and upset/deform and negatively effect accuracy.

What is "dangerous" is a cartridge that is so long that the neck is constricted by the rifling and thus wedges the bullet in the case neck.

[Doubs]

Originally Posted by DonVoigt

I"m not buying the "jump" business- unless you can point us to an authoritative source- comparing a bullet to a nail is . JMHO.

Seating a bullet to touch or enter the lands will raise pressure significantly higher than a bullet that is allowed to travel - jump, if you will - a short distance before contacting the lands.

OTOH, seating a bullet deeper into a case will reduce internal volume and also cause an increase in pressure.

Here is a link to an article written for Berger Bullets, one of the makers who cater to precision shooter. Read the article but pay attention to the text under figure 2 and the summary a little farther down.

https://bergerbullets.com/wp-content...13/03/COAL.pdf

[DonVoigt]

Doubs,
thanks for the reference.

The text you mention, from the article:
Seating a bullet against the rifling causes pressures to be elevated
noticeably higher than if the bullet were seated just a few thousandths
of an inch off the rifling.
A very common practice in precision reloading is to establish the COAL
for a bullet that’s seated to touch the rifling. This is a reference length
that the handloader works from when searching for the optimal seating
depth for precision. Many times the best seating depth is with the bullet
touching or very near the rifling. However in some rifles, the best
seating depth might be 0.100” or more off the rifling. This is simply a
variable the handloader uses to tune the precision of a rifle.

From the entire article, two things "stand out":

1-"Seating a bullet against the rifling causes pressures to be elevated
noticeably higher than if the bullet were seated just a few thousandths
of an inch off the rifling."
Noticeable is an interesting word, but means little without some numeric qualification; noticeable = observable or measurable to me- not necessarily dangerous.

2- In the long discussion of seating bullets for accuracy, including touching the rifling, Nowhere does the article say the noticable pressure increase is "significant" or
" dangerous".
A bullet seated out farther also increases internal volume- which reduces chamber pressure for a given charge.



I'm sure we can all interpret the things we read in different ways, but flatly stating that a bullet must "jump" or it will cause dangerous pressures is just not correct. JMHO.

[JTD]

I am with Don on this one. Yes it creates higher pressures. I used to shoot bench rest, and touching lands or just off was the norm for accuracy. When Weatherby designed there magnum line of cartridges, to compensate for their massive powder charge in the quest for speed, would free boar (deeper throat) their rifles for keeping pressure down. This is with bolt action rifles, so pistols are a whole other beast as strength comes into play here. If you are watching pressures, I do not see a problem, but not a pistol loading authority either. I always just stayed within the book specs, and never had an issue. The cartrige also has to cycle and function action properly in a semi auto.

[Doubs]

Originally Posted by DonVoigt

I'm sure we can all interpret the things we read in different ways, but flatly stating that a bullet must "jump" or it will cause dangerous pressures is just not correct. JMHO.

Stated that way, I agree. The pressures generated will depend upon a lot of different factors.

If you reload for it, my best advice is to be careful and tailor your load to the specific gun you use it in.

[Sieger]

Originally Posted by Doubs

https://bergerbullets.com/wp-content...13/03/COAL.pdf

Doubs,

An excellent article, though mostly a review for me.

Thank you kindly for attaching it.


Respectfully.

Sieger

[mrerick]

Well, it's great to see the theory of internal ballistics explored thoroughly.

How exactly are you all measuring your experiments with high pressure? How are you coming to your conclusions about the safety of your loads?

What instrumentation systems are you using in your reloading experiments?

How many pressure peaks are you generating with these loads? How are they spread in time?

Or... Are you theorizing in the blind? At 35,000, 40,000, 50,000 PSI is that a good idea? Something we would recommend to our forum readers?

There is a reason you do not treat reloading manuals as recipe books. It is because they are accumulated and documented evidence of measured experiments. When you change any factor from what the manufacturer documented, you are performing your own experiment.

I reloaded for over 15 years before I more formally studied this when preparing to be certified to teach the NRA Reloading Course. I've now taught that course regularly for several years. Multiple manufacturers collaborated on the material developed for this course, and I discovered many things that I thought I knew about reloading were, in fact, assumptions.

JMHO is fine for many things. I'll never rely on it when reloading for handguns and rifles. Your results may vary. If they do, I am happy for you.

This isn't about a forum participant "being right". I frankly don't care what an individual may do based on their opinion. All I can do is try and share, contribute and inform. If someone disagrees, I'm quite happy with responsible discussion. Everyone can always learn something...

I'm more conservative about reloading safety than many people. So far, I haven't destroyed a firearm with my reloads, and have helped a number of people proceed safely in an interesting aspect of our hobby.

[Sieger]

Originally Posted by Doubs

I've been loading for Lugers since 1966; both .30 caliber and 9mm. I've used just about every possible powder and bullet available. Some of the powders like Winchester 730 worked great but isn't made any longer. AA #7 leaves too many powder grains. Unique works beautifully but doesn't work well through a measure. Blue Dot and Herco work but are dirty. Bullseye and 231 are good powders and meter well. The list goes on but CFE Pistol Powder has become my go-to powder for a wide range of pistol cartridges.

Doubs,

There is a new, "modernized" Herco powder being produced by Alliant (please see their website advertising it).

To what level of cleanness this new powder will shoot in shotguns and pistols (particularly a 9mm Parabellum) is yet to be seen by me.

I weigh all of my powder charges (for both rifle and pistol shooting) with a Lyman Electronic Scale, for precision shooting with both.

With the original formula Herco powder, I haven't noticed a great deal of dirtiness with the 9mm Parabellum; whereas, Unique has always been a filthy burner for me, both in its new and older formulas.

Respectfully,


Sieger

[Sergio Natali]

[QUOTE=Sieger;332062]Doubs,

There is a new, "modernized" Herco powder being produced by Alliant (please see their website advertising it).

To what level of cleanness this new powder will shoot in shotguns and pistols (particularly a 9mm Parabellum) is yet to be seen by me.

I weigh all of my powder charges (for both rifle and pistol shooting) with a Lyman Electronic Scale, for precision shooting with both.

With the original formula Herco powder, I haven't noticed a great deal of dirtiness with the 9mm Parabellum; whereas, Unique has always been a filthy burner for me, both in its new and older formulas...
UNQUOTE


Exactly the same here, in these last ten years or so since I started reloading also for the rifles (308w and 223R) I've been using the Lyman 1200 DPS 2 Digital Powder Scale and Dispenser System, it works really well since benchrest requires extremely precise reloads. I've always used Vihtavuori powder N320 for the pistols and N135 Vihtavuori powders are rather expensive but leave the barrels pretty clean.

[Doubs]

Originally Posted by Sieger

Doubs, There is a new, "modernized" Herco powder being produced by Alliant (please see their website advertising it).

To what level of cleanness this new powder will shoot in shotguns and pistols (particularly a 9mm Parabellum) is yet to be seen by me.

I weigh all of my powder charges (for both rifle and pistol shooting) with a Lyman Electronic Scale, for precision shooting with both.

With the original formula Herco powder, I haven't noticed a great deal of dirtiness with the 9mm Parabellum; whereas, Unique has always been a filthy burner for me, both in its new and older formulas.

Respectfully, Sieger

I've settled on CFE Pistol Powder for .30 Luger, 7.63 Mauser, 7.62 Tokarev, 9mm. .40 S&W and .45ACP. It's has a burn rate slightly slower than Unique according to the burn chart and is very clean. I meter it through a powder measure and my loads are very consistent. I weigh every 10th round and am never off more than .1 grains.

Most electronic scales - yours included - are accurate to within .1 grains plus or minus. That's the same accuracy I get from my measure.

For precision rifle loads, I use an A&D EJ-123 scale that is accurate to within 2/100 of a grain. I run my loads off on an RCBS Chargemaster and then fine tune them on the A&D scale.

I go for accuracy and function. I NEVER push my loads to the max. I've never seen the need to do so.

[JTD]

Mark, watching your primer for signs of flattening worked for me. Again In modern BOLT action rifles.