We have been building our own for the last year or so . It's not actually a hard build to get close but a perfect replica is currently impossible. I used a VFC SR16E3 GBB with the correct rail from Airsoft artisan , a custom supressor and the correct furniture from magpul
The correct rail and supressor are both made already but the VFC and G&G options are better base rifles tbh . The SF version uses a ctr stock which is easier to get a replica of or even a real one if you wish