How do I unlock the following weapon parts?

#1 Posted by UnknownMemory (63 posts) -

Handgun

A220 Cdr4

3rd part on the 1st row of Capacity section after the VG4-MB2

Assault Weapons

D6B2

3rd part on the 2nd row Capacity section after the NMf-MA2

WELT-Hvy

I'm missing the whole 2nd row