Ah you started the AR discussion without me!
Oh, well time to jump in! First off, I saw someone say the current M4's have 16" barrels. This is false. The military issue M4's have 14.5" barrels. These, however, are considered short barreled rifles by the ATF and require a tax stamp and then they impose all kinds of fun limitations on you. So I'd recommend going 16" for the best mix between velocity and manueverability, at least, in a fighting rifle.
The first thing that you really should think about before anything else is what kind of gas system do you want? Carbine length like the M4? Mid length (which is in between the carbine and rifle length gas systems, it provides a more compact weapon than rifle length but less harsh recoil and slower cycling rate than carbine length)? Or Rifle length like the M16? There are pro's and con's to all three. A lot of people seem to prefer the mid-length system for a 16" barrel. If you're going with a long barrel of 18"+, I don't see any reason not to go with the rifle length system. Some carbines will need a heavier buffer to smooth out how they run, although my 16" barreled carbine gas rifle was fine stock. If you go the SBR route, you will def have some issues with running a standard buffer and extractor. And of course, you could go gas piston, if you want to.
If you're looking to make a SPR (Special Purpose Rifle) or a serious match/long range accuracy weapon, I'd go with a longer barrel in 1:7 without a doubt. 20" is considered the best for that application, although some go with 24". You certainly gain some extra velocity out of the 24" but it makes for a VERY long weapon compared to most ARs.
That said, 1:9 barrel twist is just fine for basically all shooting you'd ever need to do. I know many people that have successfully stabilized 77gr match ammo with 1:9. That isn't to say 1:7 isn't an improvement, it is, but if you find a rifle you love with 1:9, don't let it force you away. 1:9 and 1:7 will easily shoot M193 (55gr) and M855 (62gr) which are the US military issued rounds.
I would say without a doubt always get a chrome-lined barrel. They will provide you with far easier maintenance and longer life than other barrels.
If you want to go with a pre-built full AR, I'd go with a Colt 6920. If you want to buy a pre-built upper, bravocompanyusa.com has some of the best stuff out there. Companies I'd avoid buying pre-built rifles from: Olympic Arms, DPMS, Vulcan. They're all well known for having poor quality control and letting a lot of "crap" sneak out to consumers. Now, before I get flamed, that DOES NOT MEAN YOU CAN'T HAVE A GOOD QUALITY RIFLE FROM THEM. It simply means that it's a gamble, and I don't know about you guys, but I'd rather pay an extra couple hundred bucks and know I'm getting a quality weapon. I have a Bushmaster which I bought before I knew a whole lot about AR's, but it's treated me well. If I could do it over, I'd probably buy a Colt.
Like the others said, I'd always go and get a flat top rifle. As far as the carry handle ever coming off, it never did on mine before I replaced it, and I never even used tools I just kept it finger tight with the thumb screws. You can certainly use a screw driver to tighten it well beyond finger tight. In addition to that, you can use a little bit of blue loctite if you want to be doubly sure it stays. I loctite everything that could potentially fall off because that could be catastrophic if I ended up having to fight for my life.
However, Jim, if you really want an A2 then get an A2. We can't tell you what you want. We're just trying to help you get the best rifle you can for your money. A lot of people like the retro M16's with the triangular handguards. It's not for me but we all have our niche. Some of us slap all kinds of unnecessary "tactical" accessories on our guns (you might put me in that category
), others like the KISS philosophy. I like both a lot (seems contradictory, doesn't it?) so I'm going to actually be putting together another rifle and leaving it very "plain jane."
Anyway, just thought I'd share a few thoughts. If you want to get an A2, then just go get one man! You know what you want, we're just trying to help you get something that you'll love when you get it and as you find things you don't like about it you'll be able to make changes to the gun without having to start over and buying a whole new gun. The flat-top gives you that kind of versatility.
