Maybe I'm just blind, but I can't find a standard yellow machnegun ammo / rifle-magazine.

Hi, can you give me some more information on your version? On my current working branch yellow ammo is enabled by default.

I noticed it too, with K2's "more realistic guns" setting enabled, ammo is split into pistol, rifle and anti-materiel rifle, and the yellow rifle ammo recipe is disabled for some reason, making turrets impossible to use. This setting is enabled by default on a fresh K2 install.

What i checked:

Fresh factorio install only with this mod. Still no ammo.
https://imgur.com/a/h2DroId

In ver0.1.3 they are present, in ver0.1.4 they gone.

I confirm what chipgeek_jr say, without "more realistic guns" turrets switch to vanilla ammo.

I verfied on my current working branch that the yellow (pistol) ammo appears when "more realistic guns" setting enabled or disabled. My guess is that updating the military tech tree bricked here some things. I will update some of the recipes and also make some changes in tech tree.

Yellow pistol ammo works fine.
Yellow krastorio submachinegun/rifle ammo does not appear. You need them to fill first kind of turrets. Its missing in my screenshot.
I will wait for next update :)

https://imgur.com/a/dejWsw6
In 0.2 does not work :(

updated :)

https://i.giphy.com/media/v1.Y2lkPTc5MGI3NjExMmh2a2VxZTZvanByZ2JpeXlsbjB2bnhqaXJqOTR2amcyejE1N2VkbSZlcD12MV9pbnRlcm5hbF9naWZfYnlfaWQmY3Q9Zw/ZBQhoZC0nqknSviPqT/giphy.gif