Ken,
From what I gather, 8620 is an excellent choice, probably not appreciated by most. It can be core hardened up to 135 ksi (excellent strength) and casehardened together with that core hardening. So, core strength can be the same as a 4000 series steel reciever and colored per vintage guns. Also, the high chromium and nickel content give it higher corrosion resistance than traditional vintage mild steel recievers.