Personal - In an effort to fix the problems with the AR15/M16 the AR 180 type of rifle came about...
I like this series of rifles for the most part they prove far more reliable than the AR15 and much more accurate than the Mini 14 from Ruger.
Magazines are a big issue with every clone of this type of rifle they all like aluminum 20 rounders BEST, but will work with good quality aluminum magazines..
I have said before that I am not a fan of .223 but AR180 clone rifles are reliable, accurate and far superior in function and design than the AR15. This system uses an unusual multi part gas piston type operation rod. Not as light weight as the AR15 or the SU16 but far more reasonable for small people in weight than the full size rifles. Some versions have a folding stock and the folding versions when folded are shorter than a "shortie" AR 15. Ergonomics are on par with the AR 15 with a better ballance point for firing from various positions. If I had to go with a .223 this would be my "go to” rifle list.
There are many older and current production versions available, I will say a few things about the older versions not in production but will focus on the two current production clones, the ArmaLite AR180b and the Vulcan V18. The Vulcan V18 is a new rifle I bought "just to try it out", it like many others it is about to go to a new home. I would not buy a second from Vulcan, but the ArmaLite AR180b is in my view the BEST of all the AR180 clones or actual production rifles.
Function - Excellent reliable function, the older versions had to have a cut out on the AR mags or used "made for" mags - I hate cutting a good mag for this use both the V18 and AR180b use regular, standard, AR15 magazines without modification. On the Vulcan I have had FTF issues with the polymer magazines, 30 round and 20 round aluminum magazines were 100% as long as you did not push up on the magazine (causes the bolt to stop at the rear edge of the magazine). The ArmaLite rifle is a good as it gets with gas piston operation, just shy of the AK in this regard. The square bolt rides on two guide rods and has a spring return that keeps the firing pin back and the bolt head forward (less chance of twisting in movement, an issue that plagues the AR15).
Design flaws - Here is something that speaks well for the AR180 design - even Hesse/Vulcan could not "F" this design up... Oh they tried, the front gas block was tilted to the right about 6 to 8 deg. (fixable) the front hand-guards suck and the connection to the folding stock is "wiggly" (I used a hex wrench to try and tighten it, but it stayed "wiggly". The V18 has issues, but the ArmaLite company put together the Best of this design with new materials and make improvements, a top notch product. With the Vulcan V18 the flat top is so low that regular AR detachable sights will NOT work - hell you can go all the way out front and back and I was still three FEET low! No sights were included and the detachable were useless, I just attached a 2 power red dot scope...
Quality - ArmaLite was top notch, Vulcan, well let's just say that drunken Hutu natives would likely have better quality control, but like the AK you just have a hard time screwing this design up... I would choose even the V18 rifle over the Mini 14 ANY DAY.
Caliber/Ammunition - .223 is inexpensive ammunition, light in recoil, and accurate. With the AR180b even Wolf crap ammo just worked without issue, with the Vulcan almost a good as long as you did not push the magazine into the bolt face.
Use - Accuracy is about even with quality AR15 rifles, maybe lacking at most 5% in the group tightness. Easy to strip and clean (not that you need to that much) and both in current production are reliable and accurate.
Current production - ArmaLite has stopped production and the Hesse/Vulcan bunch has again changed names and who knows what they are up to, spend the extra and get one of the few ArmaLite versions.
I consider this rifle a secondary choice due to the cartridge and availability, for small folks this is nice and light weight they are not in current production but do pop up on gunbroker. They both use popular easy to find magazines (of good quality). On a side note, the Vulcan V18 was sold this weekend for a profit, with the money going into the kitty for a new rifle, avoid the Vulcan that company is actually worse in quality control than the angry beavers at Century Arms!