Many people seem to misunderstand the quality argument when talking about AR's. The majority of lower end AR's are basically of near equal quality. Lots of the "tier 3" brands make perfectly functional rifles, with excellent barrels, fit and finish etc. Good sporting rifles that most shooters will be more than happy with. It is not uncommon for those rifles to be made of the same parts and re-branded. What dirty's the water in the quality comparison, is the fact that, in the USA, a lot of AR's are bought for self defense, security, law enforcement, tactical carbine classes, even for use over seas by PMC's. This is where you get into the "tier 1" AR's, basically deployment quality rifles. Brands such as Spikes Tactical, Bravo Company, Colt, Lewis Machine and Tool, Knight's Armament, maybe even CMMG, among others. The above manufactures attempt to build their rifles to at least the lowest quality standard set out for a rifle to be accepted into service in the US military. Most of the lower end brands, do not meet this criteria, some of them not even close. This is why you see a lot of bad mouthing on the net about brands like DPMS and Bushmaster - people who need or just want deployment quality gear tend to consider them as junk.
What relevance does this have for your average NZ hunter or shooter? Probably not a hell of a lot. If given the choice, at a decent price, I would pick a "tier 1" rifle over a lower end brand any day of the week, just cuz I am a whore for the mil spec kool aid. I reckon most of the members on this board would be quite happy shooting what ever. It needs to be remembered that some of the close to military spec guns are hard to get out of the States at times, and hanging out for one over say an NEA or RRA will not really bring you much joy.
To say that "all AR's are the same" is simply spreading misinformation. Some are quite literally made out of better stuff and have better QC. I think it would be more reasonable to say - "you won't notice much, if at all functional difference between the AR brand's, within reason". I've handled and shot quite a few at varying price points, they all work the same for the kind of shooting I do.
My advice would be to find one that is as close as possible to how you want it set up from the factory, at a price you can swing, and buy it. Then shoot the crap out of it.
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