Borchardt-Luger Controversy

[unspellable]

The front toggle extension retracts the firing pin during the back stroke not for the sake of compressing the firing pin spring, but for positive control of the position of the firing pin. You don't want it sticking out of the face of the breechblock during ejection and reloading.

Since, as a side effect, the firing pin spring is compressed, it becomes a part of the overall momentum and spring compression budget.

[Kyrie]

[quote]Originally posted by Jerry Harris:
<strong>The second part of this exerpt is good as gold, but the first part is not borne out by the realities of the relationship between the toggle action and the striker. In fact, the striker spring is progressively compressed throughout the entire rearward (opening) movement of the toggle train!
</strong><hr></blockquote>

Hi Jerry!

You are absolutely right, and I stand gratefully corrected :-)

Warm regards,

Kyrie

[Jerry Harris]

Kyrie,

Thanks for your most courteous reply. Many's the time when I, too, have been grateful for a correction.

Unspellable,

I concur that firing pin control is the strongest reason for the ear's existence. What it accomplishes overall is to enhance safety by positively blocking the pin from contacting the primer at ALL times EXCEPT when the breech is within about 0.050 inch of full closure. Johnny Peppers pointed out that keeping the pin retracted also assists reliable cartridge feeding.

In his E-book on Luger mechanics (I finally got it although there's no version for Macs), Henrotin brings up a very interesting additional function for the ear. He claims that the head of the striker spring guide acts as a shock absorber by contacting the back of the frame and helping to stop the rearward breechblock travel. So the compression of the spring by the ear makes the "absorber" stiffer! Sounds reasonable, but my measurements say the spring force only increases from about 4.5 lbs to 7 lbs via the compression, and the available snubbing stroke can't be more than about 0.07 inch. I have to wonder how effective a snubber it really is.

Doubs,

When I first pondered the ear, thoughts very similar to yours crossed my mind. It is true that the effort expended by the ear in compressing the striker spring will later, as Unspellable implied, feed back as a small additional breech-closing force. But it's so wimpy (won't even overcome friction) that we probably shouldn't count it as an engineering reason for adding the feature.

[Doubs]

[quote]Originally posted by Jerry Harris:
<strong> Doubs, When I first pondered the ear, thoughts very similar to yours crossed my mind. It's true that the effort expended by the ear in compressing the striker spring will later feed back as a small additional breech-closing force. But it's so wimpy (won't even overcome friction) that we probably shouldn't count it as an engineering reason for adding the feature.</strong><hr></blockquote>

Jerry, I've pondered Unspellable's points but cannot completely agree that the PRIMARY purpose of the ear is to retract the firing pin to aid ejection and feeding. There are simply too many successful designs that, in the case of submachineguns, use a fixed firing pin or pistols with a firing pin that is pushed back by the new cartridge being chambered. e.g., the VZ-52 pistol.

My point was that the force necessary to compress the firing pin spring from it's rest position to the cocked position can not be reliably done by sear/firing pin engagement in the final movement of the toggle train as it seats the new cartridge and locks. Without the compression being provided on the recoil cycle when plenty of force is available, a reliable cocking and closure would not be possible.

I'm not downplaying the importance of safety or the benefits of the firing pin being retracted as an aid to ejection and feeding. It's just my opinion that they are secondary considerations to reliable cocking of the firing pin and closing of the action. The pre-compression of the spring also lessens the impact of the sear against the firing pin projection.... both somewhat delicate surfaces. Military primer cups are normally made harder than their civilian counterparts so a slam fire isn't likely. If that were not so, fixed firing pins combined with open bolt designs would not be possible.

As for the firing pin spring helping to soften the impact of the toggle train in it's rearward most movement, the firing pin keeper is slotted so that the toggle link to the recoil spring fits into it. The keeper does contact the link but the cushioning affect protects the link from damage due to being pounded repeatedly by an ungiving piece of steel. Any lessening of the recoil forces to the remainder of the train would seem incidental and not the primary reason for the free movement of the keeper. (Datig's book calls the "keeper" or firing pin spring guide the "breechblock end piece" which is too long to use here. Hence "firing pin keeper" or simply "keeper".)

Anyway, that's my opinion and I'm open to being convinced otherwise if the evidence is strong enough.

[unspellable]

Different firearms operate in some what different ways, including the exact details of how they feed a cartridge into position.

Most submachine guns are blow backs and many are slam fired. That is, the firing pin is fixed to the face of the breech block and the impact of the closing breech fires the cartridge. Such guns are fired from an "open bolt" position. A design of this sort depends on using blow back operation rather than a locked breech so that the exact position of the breech block (To within thousandths of an inch.) is not critical when the cartridge fires. The feed path must accommodate the fix firing pin protruding from the breech face. The usual design headache with this type of firearm is finding a way to slow down the rate of fire while maintaining reliability.

In the Luger, the feed path is such that with the firing pin protruding from the face of the breech it would block the rim of a cartridge sliding up into position. This is a key point. There was an earlier discussion on this forum about the cartridge sliding up under the extractor rather than the extractor coming forward and riding over the rim. Retaining the firing pin also prevents slam fires.

The firing pins in many of those "other" pistols are restrained by a strong firing pin spring and possibly a firing pin block. The main spring is in the frame and drives the hammer with sufficient force to overcome the resistance of the firing pin spring. The Luger is striker fired and must have the main spring directly driving the striker or firing pin.

I have seen the same article Doubs mentions about the spring guide acting as a snubber. Like Doubs, I am a bit dubious. This is one of the questions on the agenda for my project. I will be rigging tell tales to determine just how far back the action goes and whether the spring guide actually does contact the frame or recoil spring link. Part of the motivation is to determine the proper range of cartridge impulse and recoil spring strength to obtain proper functioning without abusing the pistol.

[Doubs]

[quote]Originally posted by unspellable:
<strong>Different firearms operate in some what different ways, including the exact details of how they feed a cartridge into position.

In the Luger, the feed path is such that with the firing pin protruding from the face of the breech it would block the rim of a cartridge sliding up into position. This is a key point. There was an earlier discussion on this forum about the cartridge sliding up under the extractor rather than the extractor coming forward and riding over the rim. Retaining the firing pin also prevents slam fires.

The firing pins in many of those "other" pistols are restrained by a strong firing pin spring and possibly a firing pin block. The main spring is in the frame and drives the hammer with sufficient force to overcome the resistance of the firing pin spring. The Luger is striker fired and must have the main spring directly driving the striker or firing pin.</strong><hr></blockquote>

The breechface of the Luger is recessed and encloses the rim of the cartridge. The cartridge base, therefore, cannot simply slide up the face of the breech and into position for firing. When the next cartridge is stripped from the lips of the magazine, it is being pushed upward by the ramp in front and forward by the lower part of the breechblock. When the bullet comes in contact - forcefully - with the chamber face, there is a mechanical "jump" of the cartridge upward. At the same time, the breech is still pushing forward on the cartridge and forces the nose of the bullet, as it jumps upward, into the chamber. The chamber centers the cartridge and in the final movement of the toggle train into battery, the extractor rides up and over the rim as the base of the cartridge seats in the recess of the breechface. Not until the final few thousands of an inch does the possibility exist for the firing pin to contact the primer. By this point in the feeding sequence, the sear would have engaged the firing pin and retracted it so that no contact would be possible between the pin and the primer... even if the hook wasn't part of the design.

Unlike the 1911 design that has a "controlled feed" - the rim slips under the extractor as it rides upward out of the magazine and is held against the breechface right into the chamber - the Luger does not control the feed of the cartridge and the extractor doesn't engage the rim until the very end. (If you want to break a 1911 extractor, drop a cartridge into the chamber and let the slide go forward. Unless specially modified to do so, the 1911 extractor does not ride over the rim to engage.)

While "inertia" or "rebounding" type firing pins do have a spring in front of them that must be overcome by the hammer, the VZ-52 and other Soviet Bloc designs have no spring on either end of the firing pin. The new cartridge primer pushes the pin back into firing position. The Makarov and the later SKS carbines come immediately to mind.

The design of the Luger firing mechanism, borrowing heavily on the Borchardt design, does several things to the firing pin assembly during recoil. We could discuss for years which is the "most" important or which is truly the "primary" reason for the design being as it is. All of the things it does are important to proper functioning and we'll both still have the same opinions. This has been an educational thread and I've learned a lot from it.

[Johnny Peppers]

The face of the breechblock is indeed recessed, but this in no way prevnts the cartridge from sliding up the breechface. The cartridge starts to slide up the breechface at almost the same time it begins to enter the chamber. As the cartridge continues up the breechface, it begins to push the extractor up as the back of the cartridge case and the extractor are on the same plane ahead of the breechface recess. As the cartridge moves higher on the breechface it drops into the recess and the extractor snaps down over the extractor groove in the cartridge. The extractor does not jump over the cartridge rim, but actually snaps into the extractor groove as the cartridge seats into the breechblock recess. The cartridge case begins to push the extractor up before the cartridge case is half in the chamber, and the extractor is fully raised before the cartridge is finally seated. This can be fully examined by slowly cycling a dummy round into the Luger chamber.
At the speed of the toggle assembly during firing, there is no way the cartridge itself is going to jump ahead of the breechblock into the chamber and wait on the breechblock and extractor to seat over it.

[unspellable]

First, the rim of the cartridge must rise up past the area of the firing pin, the firing pin must be held back so as not to to block it.

Second, the cartridge will be fully centered in the breechblock face before the breech block reaches battery, although by this time the sear has picked up the striker. However, what if the sear is broken and doesn't work? Then the toggle link extension controls the speed at which the striker is allowed to come to rest, possibly preventing a slam fire.

Allowing the breech block to drop on a chambered round will be hard on the extractor in a Luger too. It is not meant to ride up over the rim from the rear as a practice, although it will do so on the odd occasion.

1911's sometimes toss out cases with teardrop shaped firing pin indentations because the barrel began to drop before the firing pin is out of the way. This is generally regarded as a fault in the pistol that requires correction. In the Luger, getting the firing pin out of the way is a positive action on the part of the toggle extension rather han relying on a rebound spring.

On the other hand, since the breech block and barrel remain in line, it would not drag the firing pin over the case head on extraction in any case. There are blowback pistols that actually uses the firing pin as the ejector.

And yes, we are trying to reverse engineer the pistol and read the minds of the people who developed it a hundred years ago. And also, for every hard and fast rule, there is a firearm somewhere that violates it. As in, :There ain't no such thing as an automatic revolver." except that Webley made 'em.

[Jerry Harris]

There is still another extension or "ear" scenario which seems to me important for safety: Breech closings may jam with varying amounts of casing exposed. At about 1/4 inch from closure, the sear picks up the firing pin lug and starts the cocking stroke. At the same breech position, the sear plunger gets back under the trigger lever, so the gun will try to fire if the trigger is pulled. Suppose the breech jams with, say, 1/8 inch to go and the user, not knowing, tries to fire the next shot. The partially cocked firing pin will be released and try to hit the primer, but the ear will catch it. This will be true all the way down to 0.050 inch from full closure. So the blowback accident, although it could happen, can't occur with significant brass exposed, thanks to the ear.

Unspellable, your study of snubbing should be interesting. Did you mean Henrotin's article? (See my message to you, 6th up from here). He illustrates his discussion with photos supposedly showing impressions where the firing pin retainer head has hit the frame. He calls that normal and says it's an indicator of how much a Luger has been fired. Evidently the sides of the head reach around the spring coupling link, via the groove in the head, to make contact. I don't see any other possibility.

[unspellable]

Jerry,

Unfortunately this idea does not wash. The issue came up previously and there was a thread concerning it. I was running experiments to find the weakest usable recoil spring. The spring must store enough energy to properly carry out the loading operation, this sets a lower limit, and correspondingly, a lower limit on the load used.

With the weakest spring tried, the action occasionally stopped in just the position you are referring to. This raised the question of whether or not it could be fired so I loaded a few primed cases with the action in such a position and pulled the trigger. The Luger will definitely go bang! The amount of brass exposed is academic since the action is not locked and you are already headed for disaster.

This is a hazard to be watched for at any time, but especially if you are playing with soft recoil springs.

Sort of illustrates the difference between experiment and hot stove debates.

The bit about the firing pin retainer hitting the frame came from the electronic Luger book, I don't have it here with me at the office to quote the exact title and author, but I presume we are talking about the same one.

My project arose from the question of what to feed a 7.65 Luger. Factory ammo ain't it. The project seems to keep expanding and begins to look like it will add up to a small book by the time I am done with it. But it will be nice to have some hard numbers on what to feed a Luger and what to have for a recoil spring instead of a lot of conjecture. I am actually measuring recoil spring strength, muzzle velocity, bore diameter, etc., etc.

One fact for preliminary release: You cannot measure muzzle velocity and attempt serious target shooting at the same time. By the time I get the bullet trap lined up on the target I am invariably shooting from some awkward position that is not conducive to accuracy. And the primary point is to launch the bullet in line with the trap rather than the bull's eye. If I had a backyard range I could probably solve this problem, but I am running to the range with a car load of junk and trying to set up a tripod on uneven ground.

[Doubs]

Johnny,

The rim and base of the cartridge do not contact the breechface while being fed into the chamber until the final movement of the toggle train places the extractor over the rim. Working the action slowly enough under a magnifier lamp clearly shows a small gap between the breechface and the cartridge. The rim is held away from contact with the breechface by the forward lip of the breech and the cartridge rim rides the lip until the base is square with the breechface. Now the cartridge becomes fully seated in the chamber and the extractor enters the groove. That's when contact with the breechface actually happens.

I've never claimed that the cartridge jumped ahead of the breech or lost contact with it. I said "When the bullet comes in contact - forcefully - with the chamber face, there is a mechanical "jump" of the cartridge upward. At the same time, the breech is still pushing forward on the cartridge and forces the nose of the bullet, as it jumps upward, into the chamber. The chamber centers the cartridge and in the final movement of the toggle train into battery, the extractor rides up and over the rim as the base of the cartridge seats in the recess of the breechface."

I agree that the rim starts to elevate the extractor as the cartridge begins to straighten in the chamber but the extractor does not slip over the rim until the cartridge is fully seated in the chamber and the toggle train is in it's final 1/10th inch of travel. That, too, can be seen clearly if worked slowly enough.


Unspellable,

Because the rim doesn't contact the breechface until the cartridge is square in the chamber and seated, I'm not sure the projection of the firing pin would impede the rim. It looks as though it *might* but I don't have a defective firing pin available to experiment with. As for parts breakage, anything mechanical can and will break. The designer could "what if" himself to death and never produce a thing. They make it as safe as humanly possible and go on.

I don't agree that the Luger extractor would be hurt by repeatedly riding over rims. Looking at the design makes me believe that Georg Luger made it to do just that. He didn't have the advantage of high speed cameras for time and motion studies so it's reasonable to believe that he designed the extractor to slip over the rim as often as necessary. Many of today's best semi-autos have extractors designed that way. The Browning Hi-Power began with a controlled feed extractor but now is made with an extractor designed to slip over the rim.

[Johnny Peppers]

Doubs,
Without beating a dead horse unnecessarily, apparently we have a breakdown in terminology. The forward part of the toggle assembly is the breech bolt, and the front of the breehbolt is the breech face. On a Luger the breechface is partially recessed. The breechface must contact the cartridge in order to strip it from the magazine.

From your last post:
The rim and base of the cartridge do not contact the breechface while being fed into the chamber

During this stripping process the base of the cartridge rides up the breechface until it reaches the recessed area. As it rides up the breechface it begins to raise the extractor, and as the cartridge seats into the recessed area of the breechface, the extractor slips down over the rim of the cartridge.
I too agree, and thought that was what I said, that the extractor seats over the cartridge rim as the rim seats into the recess of the breechface. I have a feeling that the extractor functions exactly as designed. It will jump over a rim if a cartridge is dropped into the chamber rather than being fed from the magazine, but does not function and was not desighed to function that way during normal operation.

[Doubs]

Johnny, you are correct. I don't consider the leading edge of the breechblock to be the "face". Not to be contrary, but, IMO, the face is the part the cartridge base comes to rest against when the action is in battery. If the leading edge of the breechblock and the recessed face are both to be considered the breech face, we now have the same term being applied to two different planes. IIRC, I've seen the term "cone" used to describe the protective collar on the bolt in front of the face. Unfortunately, my reference books on gunsmithing do not explain "breechface" in any detail or when the face is recessed. Perhaps you have a better reference?

All that aside, I believe we both have been explaining the same mechanical actions while disagreeing on the terminology.

[Jerry Harris]

Unspellable,

Thanks -- I'm grateful to be corrected and remember your excellent test series.

By construction the ear won't let the tip of the firing pin protrude from the recessed part of the breech face until the breech is within about 0.050-inch of closure (easy to check this by measurement). So no matter what the release point was, the actual instant of your test primer ignitions must have occurred somewhere between 0.050 in. open and locked. I thought the amount of cartridge casing exposed at ignition would affect the degree of danger to the user (less being better), but maybe I'm wrong. I don't think any of us wants to do the test series that would tie that one down!

I certainly don't dispute the fact that a blowback accident could happen, as the last sentence of the first paragraph of my previous (08-22) post said.