The Missing Link ... (Updated)

... between the StG 44 and the CETME/G-3: the StG 45 delayed rollback. I've collected some photos to show the evolution from StG 44 to the G3.

StG 44 (MP44) using the 7.92 Kurz (Source)

StG 45 (M) -- A more easily manufactured firearm using a delayed roller block system (Source)

Another view of the StG 45 (Source)

Spanish CETME Mod. A (Source)

Spanish CETME Mod. B (Source)

The Spanish CETME Mod. C (7.62 NATO) (Source) (Note, this may have been made from a parts kit, since the triple frame at the front appears to be from a G3--it is somewhat slanted on the front and lacks the tab for the bayonet--and the finish is black, rather than the brown used on the CETME rifles)

An interesting variant with a a wooden pistol grip. However, it is lacking the paddle magazine release and front pin on the lower receiver, so appears to be built on a semi-automatic receiver. (Source)

Another photograph of the CETME Model C (Source) (Note: Although the stock and bayonet appear correct, the cocking handle is extra large--probably from an HK 21--the cleaning kit is German, and the magazines are German G3 magazines). The CETME cleaning kit fit into a small tube inserted into the front of the cocking tube.

An early model HK G3. Note the similarity to the CETME Mod. C (Source) 

A replica of the HK G3 with the narrow front stock and carry handle (Source)

An HK G3 sporting the Navy lower and wide forestock (Source)

The whole HK line based off of the G3 (Source)

Update: An article tracing the lineage from the Stg. 45 to the CETME Mod. C, including additional photos.