Filled the Stockpile Achievement Bugged???

Are you sure you also killed with both variants of any of the new weapons? Eg. in case of the parabellum you have kills with both the Low Weight as  well as the Suppressive variant? And the same for all other new weapons that have more than 1 variant? Getting all codexes does not say anything as you can obtain the codex by performing 10 kills with just one variant of any given gun, or a combination of multiple variants. Same logic also applies to the golden Weapon Back Side dog tags, you need 100 kills with a weapon, this can be done by 100 kills with just 1 variant, or a any given combination of available variants accumulating to 100 kills.

In that sense this trophy/achievement seems to differ from a similar trophy/achievement that came with TSNP, Maître d'Armes. For that one 1 kill with each of the new weapons (regardless which variant was used) was sufficient, but in this case it specifically mentions all variants in the description. 

If you indeed have a kill with each weapon variant and still no trophy/bugged, than it seems the trophy/achievement is bugged