I have read that bufers cause some problems with the Mini 14, like ejection/extraction .I made a buffer out of urethane and it works fine except for an occasional fault in extraction/ejection.Maybe you could try sanding it down at first.The thicker the material the greater the shock absorbtion, but I wonder how thick does it need to be? The Mini 14s is about 1/8", but I am going to sand mine down.Have you done a search of posts on "buffers" yet?