I'm just curious, what exactly do people need to see an AR 15 do to rise to the level of HD/SD worthy? I've seen, and not specifically this thread alone but it seems alot of people are quick to dismiss any sub -$600 AR as merely a "plinker" or "range toy", etc...
I fully encourage people to pursue the highest quality weapon they can afford but in terms of self defense I own guns in the lower cost bracket and they have all been 100% reliable and are made of quality materials so why would I relegate them to "plinker" status when they have proven to perform just as reliable as any other Colt, DD, BCM, etc...?
If we are talking about the distinction between a budget option and a precision target rifle I would have to agree with most in terms of paying more will result in better accuracy, etc... but for defense, I would bet an M&P Sport and a 6920 would go round for round with each other.... just a thought. I dont speak with any authority other than I have a relatively high round count with an M&P and in many thousands of rounds I have experienced 0 failures of any kind so if someone came in and brought nastiness into my home I wouldnt hesitate to use it in that role, I don't feel that I need to "level up" and get a dancing pony before I can adequately defend myself....
To be honest, I think a DPMS/Ruger/PSA/what have you is absolutely fine for HD use.
Let me clarify my thoughts on plinker-grade ARs: I don't see that term as derogatory. It seems that people have made it out to be I think of them as "toy guns", only fit for making noise unlike the heaven-sent Colt 6920. A lot of internet gun guys are like that, so I get where the derision comes from. I'm not that guy. I pinky-swear.
The fact is,
most AR shooters are plinkers; from my experience, I'd guess the number is around 90%. They go to the range once a month, they shoot 100 rounds at paper, then they pack up and go home. I personally shoot that way myself; it's fun. And if you just need a rifle to get some range time in, a DPMS is perfect. The distant screaming you hear from ARF.com is "they're not fit for DUTY!", but if you're not going to do repeated mag dumps or use your rifle as a crowbar, then who cares? Those cut corners save you up to half the cost of a Colt or BCM and you'll never notice the difference in performance.
HD, if anything, is even less demanding than range use. Your gun just sits in a corner of an air-conditioned room or a safe. It's not getting wear-and-tear, it's not getting dirty, it's just sitting there hanging around. Any gun you trust to feed reliably will work for HD. If I had a DPMS that would feed past say a 200 shot break in period (and most will), I'd be absolutely fine trusting it to HD duty. Heck, I'd be fine trusting a $150 Hi Point to nightstand duty if I was confident it would feed.
So the problem isn't that DPMSs are a bad gun. The problem is that ARs in that class are really,
really cheap to buy.
Like you said, if you need bug-eye precision or anvil-esque durability, that will cost you some money. But if you're
don't need those things (and the majority of shooters are fine without them), then $500 will buy you an essentially identical AR carbine from one of a dozen different manufacturers. If all dozen threw their 16" M4 models in a pile, you probably couldn't figure out which one was which without a roll mark. If you
shot 100 rounds out of all dozen of them, you still probably couldn't figure out which one was which without a roll mark.
So for a used gun out of that lot, cost is pretty much the only determinant you have. If the price tag is anything close to a new Smith/Ruger/PSA/whatever, then I'd personally rather just get a new rifle instead. Your run-of-the-mill DPMS carbine isn't a bad gun, it's just that cheap ARs are super fungible.