I purchased a new Colt 6920 and I would like to get some spare parts. I have read the technical threads, but am curious as to whether the H buffer is the ideal buffer or if the H2 or H3 would be even better? It seems some people prefer the H2 or H3 buffers. I have also read about Crane O rings and extractor springs, would you pick up something other than what comes in the Colt or just get stock replacements? So would it be wise to get stronger extractor springs and spring buffers and stronger recoil springs and heavier buffers as spares?