Hello, I know this isn't really an AR site, but it's the only one I am registered on. Just recently posted my introduction but since I am here; I've got a situation with a Bushmaster Predator AR-15 .223 that is short cycling more often than not. Bolt wont lock open on an empty magazine most of the time. Seems to be worse when its below 30 degrees. The rifle has a jewell trigger in it, is well broke in and has been cleaned numerous times. It's done this off and on since I bought it. I've tried different magazines and different ammo, I've even tried "specialty lubes". If I load more than one round in the mag: Sometimes it will chamber the next round. Sometimes it will partially chamber the next round and jam. Sometimes it will close and lock on an empty chamber and leave the next round in the magazine. I've checked everything I have heard of possibly being the culprit. Gas port seems to be open and large enough (.085" plastic straw easily goes all the way into and out again). Gas tube and block seem to be open and clean (I can easily blow through them and have even flushed them w/ contact cleaner). The holes in block and barrel look to be in perfect alignment. Carrier key doesn't seem to bind on tube and both appear in to in alignment. Carrier key bolts ARE tight and have always been staked. Buffer tube, buffer and spring are clean; I can't feel any binding when cycling ammo through the action by hand. Buffer weighs about 6 oz. and spring feels strong. Gas rings seem ok, bolt won't fall out of carrier and there is slight resistance to moving the bolt inside the carrier with fingers. I also stagger the gaps when I clean it. Problem doesn't seem to be related to ejection or extraction. The ejected cases all land about 3 feet from gun and close to each other. There are only very slight extractor marks on ejected cases (usually not enough to catch a finger nail on). The bolt and barrel lugs seem smooth and I don't feel any binding when engaging or disengaging the bolt with a finger tip. I've tried everything I can think of other than sending it off. I've thought that maybe the buffer is too heavy, and have heard that lighter ones are available?? Any help would be greatly appreciated. Any ideas of other easy things I can try before sending it off would be appreciated. Anyone know of a good reputable AR Guru in the Wyoming, Colorado, Montana or South Dakota area.?? Thanks in Advance and Happy Holidays.