I recently switched from a 20 inch upper to a M4gery upper, and had some extraction problems. I replaced the extractor, and it improved somewhat. I still get the occasional failure to extract, and have noticed that some of my case heads are damaged. I don't know if this is due to the shortened gas tube on my new 16 incher or what. Do the 20 inch and 16 inch gas systems use a different length of buffer? My physics tells me that a shorter gas tube would equate to a more forceful blow going into the bolt carrier due to the shorter distance the gas has to travel, thus causing the extractor to beat up on my case heads. Dos this sound right to you guys? I am using the same ammo that always functione flawlessly with my 20 incher(Q3131A and SB). Would a bigger or smaller buffer help to offset this, or do I just need to keep the buffer I have?