I probably need to find an exploded diagram and match up terms, but what does боевой личинкой mean when applied to parts of a rifle?

I probably need to find an exploded diagram and match up terms, but what does боевой личинкой mean when applied to parts of a rifle?

Never heard this term before, but I’ve looked it up - боевая личинка means “breechface” in English.

You’ve possibly found one already, but there is an exploded diagram at https://img.allzip.org/g/36/orig/2792602.jpg.