I too am not a big fan of the M16/AR platform and I've been around it for 2 1/2 decades.
I've personally witness them fail at the worst of times that shouldn't have failed. In actual combat and right at the moment they needed to work. That was in the desert and exposed to a harsh enviroment. Just as Bravo said, the M16 don't fare well in a harsh desert enviroment. And youe typical AR kool-aid drinker, to include OIF'ers will insist that it was operator error for lack of maintenance. Well let me elaborate: try to board and unboard a Blackhawk with 130 lbs of gear and it pickws you up in the desert to drop you off in the other part of the desert. Rotor wash is a bitch. Guys in Iraq now are less exposed to the desert as we were back then.
AR needs to be run 'wet', as in oiled well. When it's wet it works great.
Direct impingement has it's good and bad. The good is that it has less heavy moving parts and this helps in reducing recoil and weight, specifically a big heavy op rod.
The bad, you probably know it already, it injects hot gasses and carbon directly into the bolt.
I will attest that I've never experience or seen an AR or M16 crap out on that alone. I will add that I've seen pool issued M4's used for range purposes only packed with carbon all around the gas tube (well) in the upper receiver, bolt carriers also packed with carbon, and still function. I can't see how weapons were allowed to get that fouled with carbon but they worked. Of course I knew this because I was the one cleaning, inspecting and servicing these M4's.
Keep up with cleaning and it won't be an issue.
DUST! Dust sucks! The M16 doesn't do well with dust because in order to limit dust (AKA sand) from clogging up the action is to keep it dry. Still dust and sand get's in the action even with the dust cover close from in between the receivers, barrel, etc. Although expelling carbon has some lubricating quality, it's not ideal. Add that it needs a big ol' buffer in a tube in the but stock that is usally dry, but if sand and dust gets in there it leaves alot of bearing surface runnig friction with dust or sand in between.
AR's aren't not a 'bad' platform. In fact I do believe they are ideal as a patrol rifle. Pretty much what the guys in Iraq are more exposed to, not so much for the guys in Afghanistan. The rifle is the lightest patrol rifle used in masse, ...before everybody adds the additional 8 lbs. of stuff on it. Carry enough heavy gear strapped on to your body you too will want to carry a light carbine. And it is accurate, nimble, modular, and very gunsmith/armorer friendly and I think it's a great LE patrol carbine. What it is not is end user cleaning friendly.
And it seems as if the entire US gun market solely targets the AR platform and every rifle out there gets compared to it except the AK and Garand platforms.
That is mostly good, some bad. If you haven't hear it yet the AR is the Barbie Doll for men.
The good; you can find all kinds of parts to make the most up to date, uber tacti-cool, AR known in the history of mankind, ....for about 12 minutes when the NEXT, gotta-have-it, uber-tati-cool AR part comes out and your AR is now obsolete.
The bad; a lot of shitty and/or unnecessary parts are made and sold in the market.
MY ADVICE: The rule of thumb, specifically if you are new to AR's, keep it simple, keep it milspec (and make sure that the manufacturer is a milspec supplier of parts and that indeed you are getting that milspec part and not the "civilian/commercial" version, AKA "junk" parts - Bushmaster is known to do that). Get whatever AR from a reputable, i.e. not the really really cheap one, manufacturer. Better yet, find the sucker who paid big bucks for that AR and needs the money and get it from him. With as many AR's that are out there he'll never get what he paid, ...unless? We won't go there. Just go to the Politiking section of this forum.
I've only owned Colt's and one Bushmaster, and as duty guns all have been Colt's except for one FN. The rule of thumb USED to be to stick with the ABC brands. Armalite, Bushmaster, and Colt. The issue was that the upper and lower receivers from many other manufacturers were hit and miss as far as fitting *cough*OlympicArms*cough*. Of course stay away from Hesse, century and the other crap manufacturers.
But since then it seems hard press to find receivers that are NOT milspec cut. The only issue would be wether the finish would match up to the same color and sheen. If they don't, duracoat. I will say this, being a Colt elitists, don't get a Colt unless you want to pay extra for a company logo who doesn't give a crap about US civvy sales and won't support you.
Stag, Rock River, Bushmaster, and about a jillion other manufacturer (a new brand a week - no exsageration) they all seem to be fine. As much as I deal with EBR's it is tough for me to even keep track of who makes lowers and uppers. Haven't heard about any one going 'Kaboom!' b/c of that. Besides Colt, Noveske, LMT, Vltor, and some others are considered top of the class. Many more manufacturers make upper receivers. Never heard of any issues. More on those later.
Trigger and Hammer pins:
Colt's use a larger diameter trigger and hammer pins on the civvy AR's. If you want to avoid hassles w/getting a match type trigger, avoid Colt. Word has it that they will be going back to the smaller pins. fugem anyways.
The "anti-walk" pins. The issue was "if you shoot a lot, specially full auto, the trigger pins start to elongate". Bullshit! You and I don't have enough money to buy that many rounds and you'll go through a few barrels to get that bad. What I have experience has been a trigger pin working out and it will be hard to pull the trigger in case you hadn't noticed the pin sliding out. Just slide it back in and make sure the hammer spring engages it well that time. The other "anti-walk" pins require having to use itty bitty c clips or screws. Keep it simple, keep it milspec.
I've only used the standard military type triggers. I've shot a NM Rock River trigger. It was nice. Go with what you like best here. Hard to go wrong. Remember about Colt's pin diameter on this one.
Unless you are going non-collapsible (A1 or A2, or that other aborational short one) make sure to get the milspec buffer/stock tube. It won't matter if it's 4 position or 6. After that you can slap on whatever stock you'd like. I hear the Jenna Jamison has a CAR stock made out of latex and molded from her right tit. JK.
This is where i noticed that there are 'commercial' parts. The first time I noticed that I was like "WTF? Commercial tubes?" I hadn't realized that NOW we have a milspec and a commercial sized. I still don't know why that is. But if you have a commercial tube, a milspec stock won't go on. It's retarded, but so are many AR manufacturers and owners.
To be continued.....