the proplem with 500 S&W is the big bolt face if you want to build on a standard ak kit. now a siaga 410 SG might work as a doner. barrel blanks are $300 Aprox then you need it chamberd. the case is to short to fit a AK length mag properly and the stuff is $$$$$$$ to shoot. IMOA a 50 beowulf would be a better start if you truly have to have a 50.