All variants of the M101 (i.e. vn_b_army_static_m101_01) and D44 (i.e. vn_o_nva_static_d44) guns have hiddenSelectionsTextures defined in their configs, but do not respond to setObjectTexture.
Confirmed by Apollo, in SOG PF discord... https://discord.com/channels/824223048940519434/839848226005581845/881630013345116171