Definitely not DBT FAPC.
The wraparound design, large velcro areas and the tabs/integrated mag pouches (3rd pic on Carter, next to the chair's backrest) reminds me something like the BAE Eclipse MSPV with the MOLLE panels removed. Maybe some different attachment.
Front mag pouches also resemble the BAE M4 6-mag pouch, heavily modified (the guy with the SASS has 7.62x51 PMAGs in em)