Typo - should be wz. (for "wzór" or model) 29. (My Polish friends would never let me live down this gaff
Regarding the caption for the Chauchat, there is a very simple answer: the large capacity, straight magazine cannot properly feed the 8mm Lebel bullet because it has a rimmed case. Therefore, the Chauchat in the photo simply cannot be chambered for the rimmed 8mm Lebel.
The photo itself reminds me of one in an old reference book in my collection, Joseph Smith's "Small Arms of the World, 10th edition, publ. 1973 by Stackpole, Harrisburg, PA. The photo of the Caliber .30 M1918 Light Machine Gun, C.S.R.G. on p.377 was taken with the straight magazine propped up against the magazine well but not inserted. The rounds inside the magazine can be seen (through a slot on the side) not aligned with the chamber and the barrel.
The photo of the Chauchat with the Chinese caption is "posed" the same way. The magazine is also the same design as the one in the "Small Arms of the World" photo - straight, with smooth sides, a slot in the middle at the upper end and a bar at the bottom. Coincidence? Perhaps. Given that the caption is almost certainly wrong - one wonders if it is simply the same photo mis-labeled.
Originally, I was too lazy to scan this photo to post here and I used one found one on the internet. The photo of the .30 caliber Chauchat found on the internet has a magazine of a different design. It is slightly curved and has reinforcing ribs. The magazine is also inserted into the magazine well - that's why it is at a different angle to the straight magazine in the other photo(s).
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