Ching, i have a fully custom build Ready Fighter SLR GHK AK GBBR. I dont understand what u mean "實質接觸面積小". u are talking about the bolt or the receiver? The RF body is aluminum and i am using the GHK original bolt carrier(galvanized steel?) with Hephaestus Full Steel piston guide rod to increase the bolt weight. i put a lot of lubricated oil on both bolt and body for run in. I even installed W&S rapid fire kit. and it is running as smooth as butter oil. but i didnt fired it much, less than 1000 rounds, i just hang it on the wall most of time. and Bunny workshop did a great job on my AK installation. if u want to assemble a RF AK, u can seek for their advice. just for your reference.
