I'd hoped that I would find a civilian who owned one for a reason that went beyond, "because I have the right too, and they are fun.
OK, lets try this.
I have had a long fascination with the history of the M16. Eugene Stoner combined many design details and ideas into one design which led to the M16. That was the good part. About the only criticism (hindsight) was that Stoner did not feel the need to chrome plate the barrel and chamber even though post WW II Army research had shown the benefits of this for full auto fire. Perhaps this was because ArmaLite lacked the capability to plate the barrel. Be that as it may, Stoner developed the prototypes with cartridges loaded with IMR powder. The prototypes were very reliable with this powder. Leaving out most of the story, by the time the M16 was adopted and placed in the field (Vietnam) the Army had converted to a ball powder and the 5.56mm M193 Ball cartridge powder formulation contained a shelf life extender (Calcium Carbonate - CaCO3) at levels far above those necessary to clog the rifle's gas tube. The early combat history of the M16 in Vietnam was marred by this problem. The gas system Stoner employed, while very simple and direct, allowed for contaminates from the powder to be blown back into the reciever/bolt area.
From external source: (http://forums.beyondunreal.com/archi...p/t-88840.html
The use of ball gunpowder left a very sticky residue in the barrel and the gas tube of the M16. Since the barrel wasn't chrome-plated and no cleaning equipment and/or lubricants were available, it hardened quickly and soon made the rifle inoperable. The residue also caused spent casings to become stuck in the chamber and the rifle suffered a rim shear extraction failure, where the bolt's extractor tore off a portion of the end of the spent casing, leaving the rest of the case stuck in the chamber.
In retrospect, the "forward assist" of the M16 may have been less than necessary.
If you made it this far, I had a desire to personally examine the historical M16 problem but not necessarily reproduce it. Thus, I went through the hoops to acquire an M16A1 (But I wanted the chrome bore version because of the first paragraph above.) After going to all that trouble, I am certainly not going to abuse the "test item". Instead, noting that IMR powders were the design basis for the M16, I made various tests to verify the reliability claims versus the IMR powder claim. My test results were very satisfying and may one day make a good "historical editorial piece" somewhere. The most notable result is that loading for semi-auto function and full-auto function in this gas gun is not the same thing at all.