Jack;
Beginning with the John Browning designed model 1886 Winchester the lever was connected to locking bolts which fit in grooves in the sides of the receiver. Opening the lever dropped the bolts releasing the Breech bolt & closing it raised them either behind the Breech bolt or in grooves in its side. This resulted in a much stronger locking than the toggle linkage design of the earlier models. Winchester did not have an action capable of containing the .45-70 Govt cartridge until Browning designed the 1886 action for them. The 1876 was also a toggle action, don't recall off hand if there were any others or not. The 1886, 1892, 1894 & variants of each as well as the 1895 all had the stronger locking bolts.
The dropping block rifles are secured by the receiver walls behind the block, they only have to be held up to remain closed, but there is virtually no downward force on them in firing.
