Hey there again 308/338 -- Thought I'd toss in some more information for your consideration. Now the following is about the 1876 rifle, it's based on the 1873 toggle action and is essentially the same thing, just for rifle calibers instead of pistol calibers.
The strength of the Model 1876 rifle and the .45-75 W.C.F. cartridge was tested by Winchester in the late 1870s. These tests will astound collectors and shooters who have stated the Model 1876's toggle link action is "weak". The factory conducted tests on the strength and reliability of the action to answer concerns by customers. In response to a letter sent to the company by Charles Hallock, Esquire, of Forest & Stream magazine, Oliver Winchester responded by telling about the tests the factory accomplished on the 1876 rifle. He indicated that engineers first started the tests by removing one of the toggle links and fired 20 rounds (this was with .45-75 W.C.F. cartridge with 350 grain bullet) with no effect. They restored the missing link then went through 6 more trials starting with a charge of 105 grains of black powder, behind a 700 grain bullet! The comment "worked well" is noted. They then increased the charge of powder to 165 grains behind 3 bullets (1,150 grains) and that "worked well." From there, they increased the powder charge to 203 grains and added more bullets until they reached 1,750 grains of lead (five 350 grain bullets). This also "worked well." Finally, they added one more bullet, bringing the total weight to 2,100 grains, and things began to happen. The comment was, "Breech pin slightly bent. Arm working stiff." The seventh and final test was again 203 grains of powder but this time six Martini bullets weighing 480 grains each (2,880 grains) were used. "The charge bent the breech pin, blew out the side plates, split the frame and otherwise disabled the arm," was the comment. Oliver Winchester noted that in this seventh trial, the shell had burst into fragments and the escape of gas at the breech did the damage.
Every time I read this it astounds me, that's for sure. Here is what they are talking about. This is my 1873 with the side plate removed. Removing just one screw gets you this far. The toggle link is two tone, silver on the barrel end and black on the hammer end.