Early M91/30 bolts were identical to M91 bolts - the bolt handle was thicker towards the bolt body. In 1933 a new construction was designed. The bolt body and the handle became two separate parts which were welded together. Previously, they were one piece. This design change was implemented into production in 1934, both designs were in production up to 1935, at this timethe production of early pattern was stopped.
Early style bolt body with a handle that's thicker towards the bolt
Late style bolt body with a handle of universal thickness
Excerpt from drawings which show two bolt body parts
Wartime Izhevsk bolt with welding traces that were not polished
The only clearly visible change in cocking piece construction during all of the M91/30 production period was the change of the cocking knob shape and size - in Autumn of 1941 the Izhevsk factory simplified its shape. The diameter was changed from 1" to 0.9", cutout areas on the bottom were eliminated and the shape of the cocking knob became round. Interestingly, this design was only produced by the Izhevsk factory. The Tula factory #536 NKV in 1942-1943 still produced the prewar pattern, but it seems that in 1943 it moved to the Izhevsk pattern. At the moment it is difficult to make a final conclusion because factory matching 1943-1944 Tula rifles are almost non existent. If you have something to add, feel free to contact me.
On the left - simplified Izhevsk cocking know, on the right - standard prewar design.
Bolt head, connector bar, firing pin & spring
Parts such as the bolt head, connector bar, firing pin and firing pin spring had no major changes during the M91/30 production period. The only thing that can be mentioned is the placement of the factory markings. In December 1937 changes to the drawings were adopted, they moved the location of the factory marking on the connetor bar from the top to the side. Interestingly, Izhevsk never introduced these changes into production, and continued to stamp the marking on the top. Tula moved factory markings starting in early 1938.
Standard pattern of the factory marking on the connector bar
Tula pattern of factory marking on the connector bar - starting in 1938.
Ejector and interrupter
In the initial period of M91 production, starting in 1891 and up to the 1935, a one-piece ejector-interrupter was used. In 1908 its shape was slightly updated because of the adoption of a new bullet shape (M1908 light bullet). This design change is very difficult to see, you need to compare a part made with the old design side by side along the updated one.
At the top - new design, at the bottom - old
After adoption of the M91/30 ejector-interrupter, it was was left untouched, being updated only during general optimization of production in 1935. The first year when a two-piece ejector-interrupter, which was much more simple to manufacture, was implemented into production was 1935. Its construction was the same up until the end of production of M91/30 rifles and M38&M44 carbines.
Two-piece ejector-interrupters can often be found without factory markings, these parts were issued by Main Artillery directorate repair depots as replacement parts.
One piece ejector-interrupter
Two piece ejector-interrupter