toggle link action strength

[dpsurveyor]

I am puzzled.
Some say the toggle link is a very weak action and should not shoot +p loads. I believe they are talking about too much pressure against the bolt face.

What about the sides of the brass obtruating (sp?) against the sides of the chamber and minimizing the backward movement of the cartridge?

I have read it both ways and would appreciate your opinions. I own and shoot a Uberti 1860 Henry in 45 colt and it is a beautiful rifle. I don't want to ever mess it up even by accident.

Shoot straight and stay safe.

 

[briansmithwins]

The cartridge case frictions against the chamber can reduce bolt thrust, but you really shouldn't count on it, as water, oil or grease on the ammo can will reduce the friction, sometimes greatly.

As for the strength of the action and the feasibility of shooting high pressure loads, I'd contact the manufacturer and go with what they say. The toggle link action is weaker than bolts that lock up directly into the receiver, but how much weaker when executed with modern steel is a engineering question that I can't answer.

BSW

 

[mavracer]

I wouldn't load +p 45 Colt in a 60-66-73 action, 38 Special maybe. Even if it didn't blow up you would significantly shorten life of the action.

 

[eastbank]

winchester did a blow up test on their 1876 and it was surprizing how much that over grown 1873 took. eastbank.

 

[Tommygunn]

I wouldn't load +p 45 Colt in a 60-66-73 action, 38 Special maybe. Even if it didn't blow up you would significantly shorten life of the action.

Uberti chambers their Winchester 1873 in .357 magnum, so >atleast that version< of the '73 can take the pressure.
Remember, today's metallurgy is much better than what was available in the 19th century. That would make some difference.
OTOH many experts who've written about the toggle-link Winnies have state that the design is not the strongest. The 1876 took the design about to its maximum limit, and recall it was when Winchester bought John Browning's 1886 design that the first true Winchester that could take the big loads of that day was marketed.
As for 45+P in a toggle link, I'm gonna do the lawyer thing and say; follow what the manufacturer says to use in it.

 

[lysanderxiii]

There is a big difference between "weaker" and "not strong enough". 550 cord is weaker than 1/2 braided nylon rope, however both will hold up 500 pounds.

However, I would differ to the recommendations of the manufacturer.

 

[mavracer]

Uberti chambers their Winchester 1873 in .357 magnum, so >atleeast that version< of the '73 can take the pressure.

Since bolt thrust is a product of pressure X case ID, bolt thrust between standard 357 and standard 45 Colt are going to be closer than pressure alone would indicate.

I'd still caution against using Buffalo Bore, Underwood, Double-tap 357 ammo in a toggle link action.

 

[dpsurveyor]

Thank you all for your responses.

I don't ever intend to deliberately overload my Henry. I am worried that someday I could make a mistake reading the scale or doing some other dumb thing that might cause a problem with my rifle. There are times when two plus two are going to equal five no matter who you are. I was just wondering if I had any "cushion" to fall back on built into the rifle. I keep my reloads well away from the max loads listed in "the book" and always look it up at the beginning of every reloading session.

I am careful and always double and triple check my reloads to be sure I don't mess up. Don't want to be making any pipe bombs, ya know?

 

[RecoilRob]

To make a toggle link function the pieces have to move rotationally with one another and this requires an axle or pin. If very much clearance is left in the rotating joint all the pressure will be born by this axle/pin and might limit how much it will take and how long it will last. The Martini-Henry block rotates on a pin at the rear but is designed so that when it's up in locked position it's hard against the rear of the receiver to take the thrust. If the block isn't fitted properly the pin will be stressed and can fail.

You certainly could machine the joints to have full surface contact which would make it virtually as strong as a solid bar of steel...but the machining difficulty makes such a thing more expensive. Thinking Luger here and strength will depend on the particular example whether it'll hold up to high pressure or not.

Didn't the Pedeson rifle have problems with primary extraction which forced them to use a lubricated case? Without the case obturation to help reduce the bolt thrust such a thing might place more stress on the joints than a more conventional case/chamber relationship.

 

[barnbwt]

There is a big difference between "weaker" and "not strong enough". 550 cord is weaker than 1/2 braided nylon rope, however both will hold up 500 pounds.

Toggle link guns can be quite strong --see the Maxim or Vickers, for instance, which fired full-on HMG cartridges like 8mm. What they are not, however, is stiff. Because of all the linkages, and the parts that transfer load to each other through axles in shear, and ultimately the great distance between the breechface and the final stop for all that bolt thrust load into the receiver, you have to make the thing quite beefy to avoid problems with case deformation in higher pressure cartridges (especially bottle-necks, which will tend to get stuck if allowed to stretch while under pressure). Even then, broken-case removal tools were common on the heavy MGs, since even they allowed a certain degree of play in the headspace upon firing (loose chambers and poor timing were the primary factors, though)

But in WWI and immediately prior during all the trench warfare, the necessary weight was a blessing in disguise in that it allowed the machine guns to dissipate and absorb far more heat than can be expected with today's designs. It was not uncommon for gun barrels to be sized large enough, that when heated to glowing dull-red by gun fire, the radiated as much heat as they generated, able to fire indefinitely. Others more directly cooled the guns using water, allowing them to function more like combustion engines than weapons. And that's how that one Vickers was able to fire a documented +1 MILLION rounds in 24hr period; almost continuous fire over the opposing trenches.

IIRC, the later lever guns like the 1895 Winchester added secondary locking mechanisms that more directly tied the load-bearing breechblock/bolt to the receiver, leaving the toggle/lever system to operate the system rather than restrain it. This was the ultimate solution to getting the biggest bang out of a given working mass/volume using a lever system.

TCB

 

[Slamfire]

Toggle link guns can be quite strong --see the Maxim or Vickers, for instance, which fired full-on HMG cartridges like 8mm. What they are not, however, is stiff. Because of all the linkages, and the parts that transfer load to each other through axles in shear, and ultimately the great distance between the breechface and the final stop for all that bolt thrust load into the receiver, you have to make the thing quite beefy to avoid problems with case deformation in higher pressure cartridges (especially bottle-necks, which will tend to get stuck if allowed to stretch while under pressure).

I agree. The toggle link breech is inherently unstable which is why the thing was used in delayed blowback actions. If you get the thing out of line, it opens!

The toggle actions used in Winchester rifles, if you look at the things you see load being carried by pins. Whatever is weakest in the locking mechanism, that is what is going to fail first. Given the slack in the components and all that, I don't consider the Winchester toggle action rifles all that strong and historically, they were not.

 

[Slamfire]

Didn't the Pedeson rifle have problems with primary extraction which forced them to use a lubricated case? Without the case obturation to help reduce the bolt thrust such a thing might place more stress on the joints than a more conventional case/chamber relationship.

The Pedersen rifle did not have "problems" with primary extraction, it was designed to use a lubricated case because it was a delayed blowback.


As Hatcher himself explains:


Army Ordnance Magazine, March-April 1933

Automatic Firearms, Mechanical Principles used in the various types, by J. S. Hatcher. Chief Smalls Arms Division Washington DC.

Retarded Blow-back Mechanism………………………..

There is one queer thing, however, that is common to almost all blow-back and retarded blow-back guns, and that is that there is a tendency to rupture the cartridges unless they are lubricated. This is because the moment the explosion occurs the thin front end of the cartridge case swells up from the internal pressure and tightly grips the walls of the chamber. Cartridge cases are made with a strong solid brass head a thick wall near the rear end, but the wall tapers in thickness until the front end is quiet thin so that it will expand under pressure of the explosion and seal the chamber against the escape of gas to the rear. When the gun is fired the thin front section expands as intended and tightly grips the walls of the chamber, while the thick rear portion does not expand enough to produce serious friction. The same pressure that operates to expand the walls of the case laterally, also pushes back with the force of fifty thousand pounds to the square inch on the head of the cartridge, and the whole cartridge being made of elastic brass stretches to the rear and , in effect, give the breech block a sharp blow with starts it backward. The front end of the cartridge being tightly held by the friction against the walls of the chamber, and the rear end being free to move back in this manner under the internal pressure, either one of two things will happen. In the first case, the breech block and the head of the cartridge may continue to move back, tearing the cartridge in two and leaving the front end tightly stuck in the chamber; or, if the breech block is sufficiently retarded so that it does not allow a very violent backward motion, the result may simply be that the breech block moves back a short distance and the jerk of the extractor on the cartridge case stops it, and the gun will not operate.

However this difficultly can be overcome entirely by lubricating the cartridges in some way. In the Schwarzlose machine gun there is a little pump installed in the mechanism which squirts a single drop of oil into the chamber each time the breech block goes back. In the Thompson Auto-rifle there are oil-soaked pads in the magazine which contains the cartridges. In the Pedersen semiautomatic rifle the lubrication is taken care of by coating the cartridges with a light film of wax.

Blish Principle….There is no doubt that this mechanism can be made to operate as described, provided the cartridge are lubricated, …. That this type of mechanism actually opens while there is still considerable pressure in the cartridge case is evident from the fact that the gun does not operate satisfactorily unless the cartridges are lubricated.

Thompson Sub-Machine Gun: … Owing to the low pressure involved in the pistol cartridge, it is not necessary to lubricate the case.
“Blow-Forward” Mechanism: We have seen above (blowback mechanism) that some method must be provided to hold the breech block against the barrel when the gun is fired, because otherwise the pressure of the powder gas pushing back on the cartridge case would drive the breech block back away from the barrel and let the cartridge out while the explosion was going on. With the blow-back gun the breech block is allowed to move in this manner, but is made heavy enough so that the movement does not occur too quickly.

Instead of allowing the breech block to move back, it would be quite possible to attach the stock and al the frame-work of the gun firmly to the breech block and then allow the barrel to move forward when the gun is fired instead of allowing the breech block to move back. Several automatic pistols, notably the Schwarzlose, have been constructed on this principle.

In 1917 an inventor appeared at Springfield Armory with a machine gun made to fire the Krag army cartridge, having the framework of the gun solidly fixed and the barrel loosely mounted so that it could move forward against the action of a spring when the gun was fired. This gun operated, but it was necessary to grease the cartridge case to prevent the front part of the case, expanded by the pressure, from sticking to the barrel as it moved forward.
One trouble with this system is that it greatly accentuates the recoil. The normal tendency of the explosion in the cartridge case is to push the bullet in one direction and the cartridge and breech block in the other. When there is no provision for locking the breech block to the barrel but instead it is attached to the framework and stock of the gun, and the barrel left loose, it is obvious that the explosion drives not only the breech block but the stock to which it is attached back against the shooter’s shoulder with a considerable amount of violence.

This inventor had besides his machine gun, a semiautomatic shoulder rifle built on this principle, though the mechanism was only crudely worked out. He demonstrated this gun by firing a number of shots with it and then allowed the Armory officials to fire it. I fired one or two shots with it and the kick was so terrific that I felt as though a mule had landed on of his hind feet on my shoulder. I seemed to be kicked back two or three feet from where I was standing and tears actually ran out of my eyes from the blow, which marvel as to how the inventor, who was a frail, pathetic looking man, managed to shoot it without any signs of discomfort. After showing his model he returned to a nearby factory to complete the mechanism but a few days later we were distressed to learn that he had taken his new gun and deliberately blown his head off with it. Probably the kick was too much for him after all.


This is Pedersen's patent on his wax lubricant:

Patented Nov. 4, 1930

PATENT OFFICE JOHN DOUGLAS PEDERSEN, OF SPRINGFIELD, MASSACHUSETTS

http://www.google.com/patents/US1780566

In the preparation of cartridges having metal cases for storage and for use, it has been found desirable to apply to said metal case a relatively thin coating of some protective substance which will preserve said metal case for comparatively long periods of time against-deterioration, such as season cracking. In the present invention, the material for said coating has been so chosen as to perform the additional function of acting as a lubricant for the case of the cartridge, both for facilitating introduction into the chamber of the gun and the extraction thereof after firing. The most suitable wax which I have found for this purpose and which I at present prefer is ceresin, a refined product of ozokerite; but I wish it to be understood that other waxes having similar qualities may exist which might serve equally well. Some of the desirable features of ceresin are that it is hard and non-tacky at ordinary temperatures having a melting point somewhere between 140 and 176 Fahrenheit. It is smooth and glassy when hard and does not gather dirt or dust. However, when the ceresin on the cartridges is melted in the chamber of a gun, it becomes a lubricant.

Other lubricating waxes have been employed for coating cartridges, and the method most generally pursued for applying said coating to the cartridge case has been to prepare a heated bath of a solution of the wax in a suitable solvent, dip the cartridges therein so that a film of the solution will adhere thereto, and finally withdraw the cartridges to permit the solvent to evaporate from the coating film. This former process is comparatively slow and has been found lacking in several important respects.


Incidentally, this was a delayed blowback mechanism, and it used greased cartridges! All of the Oerlikon actions were based around this concept:

 

[35 Whelen]

Funny...I think when people think of toggle link actions, they think of loose, rickety, sloppy, clattering devices barely capable of handling BP cartridges of 130 years ago. Makes me doubt many have ever even taken a close look at one of these actions. So, here's a look at the internals of my Uberti '66:



I can assure you there is ZERO slop or play in the toggles and pins and everything must be lined up just perfectly to remove or replace the toggles. As one can see the toggles bear 100% against one another and at the rear of the receiver against the big chunk of brass.

Now here we see my 1873 Uberti chambered in (GASP!!) .44 Magnum:





I also find it interesting that folks think nothing of Rossi chambering their copy of an 1892 Winchester in 454 Casull, but grow faint and begin to calculate bolt head thrust, etc. when the subject turns to Uberti chambering their copies of the 1873 in .357 Magnum or .44 Magnum.

Back to the '66...mine is chambered in 44-40 and the load I settled on a charge of Unique that propels a 220 gr. cast bullets 1300 fps. I've fired several hundred rounds sice I got the rifle last January and she's as tight as ever!

Uberti's manuals state simply that their firearms are to fired only with ammunition that falls within SAAMI pressure specifications. Stick with 14,000 psi loads and you'll be fine. Mind you, loads in that pressure realm out of a 24" rifle barrel are going to be capable of some serious velocities if a fella chooses the proper powder.

So there you are!

35W

 

[eastbank]

i load my original 1876 made in 1883 in 45-60 with a cast 350gr bullet with 27grs imr 4198(1300 fps) and have incountered no problems at all and have killed deer with it. eastbank.

 

[lysanderxiii]

Incidentally, this was a delayed blowback mechanism, and it used greased cartridges! All of the Oerlikon actions were based around this concept:

The Oerlikon 20mm/70 was a straight blow-back, there is no delay....

The Oerlikon and the MK-108 were straight blow-back designs. There is no delay between firing and the movement of the breech face. They did use rebated rims so the bolt could follow the base of the round inside the chamber and used a very long headspace to support the case longer, but that is not a delayed blow-back

A delayed blow-back design delays the motion of the breech face by mechanical disadvantage, as shown:

 

[Steve S.]

My '73 Miroku toggle link action appears to be very well machined with very tight tolerances; I "think" that this modern rifle made with modern steel is probably capable of exceeding SAAMI pressures of 14K for this design but I have no reason to venture into that territory - I simply do not have the expertise to go there. So I stick with the SAAMI limits and enjoy shooting this rifle very much - fun rifle to shoot.

 

[35 Whelen]

I have absolutely no doubt the metal used in current production '73's is much harder than that used 130 years ago. In fact if I'm not mistaken, back then the receivers were made of iron, not steel.
I have two old original Winchesters, 126 and 130 years old, and wish I had a way to test the hardness of the receivers and toggles vs. Uberti's.

35W

 

[Malamute]

Back to the '66...mine is chambered in 44-40 and the load I settled on a charge of Unique that propels a 220 gr. cast bullets 1300 fps. I've fired several hundred rounds since I got the rifle last January and she's as tight as ever!

I agree that the toggle action type Winchesters are stronger than most believe, but,...you must realize that several hundred rounds is hardly a drop in the bucket to many serious shooters, and not a challenge to the gun.

Steve Young of Steves Gunz, has said hes seen a number of 66 and 73 Ubertis that have been in fact worn out, or at least worn noticeably loose from cowboy action shooters using them. He also said the 357's seem to loosen faster when used with full power factory loads. The guns don't hold up as well or as long as the 92 actions. That doesn't deter me from liking them or wanting another one day, but puts some perspective on it.

With most lever actions that are overloaded, they tend to loosen up rather than blow up. Blow-ups are a different phenomenon, and can affect any of them. The barrel seems to be the breaking point though, not the action lockup. Same as revolvers tend to com apart at the cylinder locking bolt, then its a chain reaction of other parts following.

Ive heard of toggle actions blowing the sideplates off, but I don't recall the reason, it may have been a case that let go. The bolt didn't launch through anyones head as is often claimed will surely be the result of a 73 type action is ever overloaded in the slightest way. I have heard of one firing pin extension (that's the piece sticking out the back, it isn't the bolt) coming apart in a gun failure. There was an injury I think, but not a fatal type one. The actual bolt is contained in the frame. Its hard to imagine how it could fit through the small opening of the firing pin extension in the back of the frame.

 

[gwpercle]

A brass framed 1860 Henry is probably best served with standard velocity ammo.
Brass is softer than steel ! Reguardless of the action. Heavy loads will batter it .
P-08 Luger has a toggle action...but it's constructed of steel .
Load Safe
Gary

 

[lysanderxiii]

I agree. The toggle link breech is inherently unstable which is why the thing was used in delayed blowback actions. If you get the thing out of line, it opens!

The toggle actions used in Winchester rifles, if you look at the things you see load being carried by pins. Whatever is weakest in the locking mechanism, that is what is going to fail first. Given the slack in the components and all that, I don't consider the Winchester toggle action rifles all that strong and historically, they were not.

Toggles can be extremely stable, go over top dead center with a buttress on the links to prevent over-rotation, they aren't unlocking, no matter the load. If you look at any toggle lock design the toggle rotates to just over dead center and then stops, careful examination will reveal that they are actually .5 to 1 degree over center. The toggle will not break until the joint is rotated a degree or two.

The "weakness" of a toggle lock is the fact that there are three rotating joints, and since they are rotating joints the have three point contacts, each taking the entire load. Point contacts under high loads leads to very high stresses on the material.

The same "weakness" is also present in any of the "flapper" locks, like the Goryunov, BAR or MAG-58, only they have one rotating joint in these cases.

Shearing a pin (if it is designed properly) is extremely unlikely; however, loosening up due to elongation of the holes is a distinct possibility.

The delayed blow-back of the Pedersen was an interesting application of a toggle that never was positioned in the dead-center (or over dead center), but always slightly broken. The trick was the two links of the toggle were not pinned together, but contacted each other on a cam surface, and the shape of the cam surface was such that as the toggle broke, the contact surfaces remained very close to the axis of the bore so the moment trying to open the toggle was always very small.

The other major delayed blow-back toggle design was the Schwarzlose worked slightly differently, the toggle was not open and lying flat, but closed with both arms superimposed and nearly horizontal, upon firing, the toggle had to unfold, and at full bolt movement was open and flat. Having the toggle closed and horizontal achieved the same purpose as the complicated cam surfaces used by Pedersen, it holds the moment trying to open the toggle small, until the pressure has dropped.

 

[35 Whelen]

I agree that the toggle action type Winchesters are stronger than most believe, but,...you must realize that several hundred rounds is hardly a drop in the bucket to many serious shooters, and not a challenge to the gun.

I shot CAS locally for a couple of years so am.well aware of the rigors to which the firearms are subjected. I think you missed my point...it was not that several hundred rounds were a realistic test of the mechanical integrity of the rifles in question, rather the LOADS that have been fired through it. If you'll notice I stated I'm running a 220 gr. bullet at 1300 fps, a load that exceeds the original by a pretty good margin.

I own a '66, three '73's and a '92 and have been through all three types. The '92 has far more moving parts and isn't nearly as simple as the '66 and '73 so it's hard for me to believe it's more rugged. If this were the case the '92 would be the rifle of choice among CAS competitors, but it does not appear to be, rather it's an I expensive way to get in to the game.

35W

 

[Malamute]

I own a '66, three '73's and a '92 and have been through all three types. The '92 has far more moving parts and isn't nearly as simple as the '66 and '73 so it's hard for me to believe it's more rugged. If this were the case the '92 would be the rifle of choice among CAS competitors, but it does not appear to be, rather it's an I expensive way to get in to the game.

I believe the choice of the 66 and 73 is more about the action jobs available for them rather than the ruggedness of the actions. The load you use is still black powder level basically. Running a 200 gr at 2000 fps was a standard load for 92 actions in the old Lyman manual for many years.

I haven't heard about 92s loosening up the same way that 66/73s do when used a lot, other than the 454's can loosen in time if enough factory level loads are shot.

I don't dislike the 66/73s at all. I don't think they are weaklings, but they also are not in the same class as the 92 action for general use.

Edit: Black powder 44-40 loads http://castboolits.gunloads.com/showthread.php?265478-My-44-40-Black-Powder-Journey

Lyman manual No 45 page for 44-40

 

[mavracer]

I own a '66, three '73's and a '92 and have been through all three types. The '92 has far more moving parts and isn't nearly as simple as the '66 and '73 so it's hard for me to believe it's more rugged. If this were the case the '92 would be the rifle of choice among CAS competitors, but it does not appear to be, rather it's an I expensive way to get in to the game.

CAS shoot a lot of mouse phart loads, 220@1300 isn't a lot more than the original load a lot more would be the 300gr @ 1500 that I shoot from my 16" 92 44 mag

 

[35 Whelen]

OK but we're talking two different subjects here. One is action strength where pressures are concerned, the other mechanical reliability over time.

Regarding the former, the fact that the '73 actions are now being chambered in .44 Magnum should put to rest any arguments regarding strength. As strong as the '92? No, but plenty strong for the cartridges chambered. I'm going to try to find the article in which Winchester attempted to blow up on of their toggle link (1876) actions.

As far as how long the '73's will last, why guess? Ask! There are throngs of folks using them every week in competition. I asked a buddy of mine who shoots almost weekly, how his '73 had held up. "About 15,000 rounds so far." All that's been replaced is a broken firing pin. Sounds pretty reliable to me.

35W

 

[Malamute]

I'm familiar with the 76 test. Pretty interesting. Still black powder loads, but interesting. Post it if you can locate it, Id enjoy reading it again.

In this case, the action strength and mechanical reliability over time are related if the action loosens up from extended use with regular level loads in 44-40 class or factory level 357s. Id truly like a 73 in 357, but wouldn't expect it to last as long as a 92 action if heavy factory level loads were used in it extensively.

15K isn't bad. Sounds like his is getting along great. I don't know if Steve Young mentioned a round count on the guns hes seen that have loosened up. The level of the loads did seem to have a bearing on how long they lasted, if I recall correctly.

I had one of the Navy arms 22 cal 66's, I don't know how many rounds I put through it, but it was a fair number. I was shooting 2500 rds/mo through it for a while. Tremendously fun gun. I really miss it. Wanting a Miroku 73 at some point.