I'm sure this will annoy some people on here, but I want a permanent home for these questions & Devils advocate responses. Instead of re-typing them to defend my position in a random thread, I can now just reference this thread (if the mods let me keep it? 
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But it doesn't use STANAG or AK-47 magazines.
I understand why the first one is important to folks. The biggest reason is standardization and many different guns were created to use them, but the downside to that is not all guns have excellent compatibility with every manufacturer. At least with a proprietary gun with its own magazine, you're pretty much guaranteed it's going to work. 'Not always, but mostly. CZ has made some questionable OEM mags of late, but that's a rarity.
The AK-47 complaint however annoys me the most. So when looking at another 7.62x39 gun (like the Vz.58), people frequently complain it's not worth it because it is not compatible with one of the WORST aspects of an AK-47? AK mags suck. I said it. The fact a gun doesn't use them is a plus in my book. No BHO makes them very outdated. The also suffer from the same problem that QC is a crapshoot - not just because of magazine quality, but AK-47 quality. The same is true of any random 1911 gun and magazine.
The AR-15 is not proprietary. I like non-proprietary guns.
Isn't that true of most guns, especially pistols? So you don't own SIG's, Glocks, S&W, Ruger, bolt actions, shotguns? If you take this stance, you better only own AR-15's, AK-47s and 1911's.
Parts availability in an apocalypse.
Where exactly are you planning on buying parts in such a scenario? If you don't have spare parts on hand, then Brownells or MidwayUSA aren't going to be shipping. Gun stores will be closed or looted. If that's not the case, then you have a different definition of apocalypse or TEOT than me.
Secondly, if you think having an AR-15 is important because you can scrounge AR-15 parts off other people, that seems unlikely. If you come across a fallen comrade with an AR, just take his! It doesn't seem like repairing and piecing together guns is something we'd have time for.
If you mean parts availability because you personally own a dozen AR15's so that provides you with a built-in spare parts inventory? True, that does. But the same can be said of buying a dozen of any other gun too.
The company might go out of business, so how will you get parts?
This is frequently lobbed at AR-15 piston alternatives like PWS, POF, Adams Arms. True, but then isn't that also true of any company that isn't a maker of AR-15's, AK-47's and 1911's? At least with the AR-15 design (one of its best aspects) you can simply buy a different upper if that issue comes to pass. But this argument is basically true of any company. It can be said of a SCAR or ACR too. Let's not forget than even SIG has been known to abandon guns in favor of a new design and they're a BIG company. I've never had a problem with PWS. And I haven't even touched upon old, rare surplus guns. Nobody seems to have an issue buying those.
If AR-15's were meant to have pistons, they would have been designed that way.
If a piston variant AR-15 has a piston, then it was designed to have that piston. The question is a non-sequitur. How is that different than a SIG MCX or SCAR, or my PWS MK116? If it works, it works, In many cases it's an improvement. I mean, AR-15's weren't designed to have 7.5" barrels but companies manage that. Surely that should catch the same ire from purists? What about .300BO and all those other calibers that weren't designed for an AR? Aren't those abominations too? They also aren't great with suppressors but people modify their guns to handle that too - albeit with some powder blowback in the face. 'Doesn't seem like you should do that if it wasn't "designed" for it.
Direct impingement is fabulous.
Is it? Why doesn't anyone else (today) use it besides Stoner derived guns? Why do most of the new semi-auto rifles these days use piston? I know this is a common link that is pointed out, but he ain't wrong.
https://www.readyman.com/blogs/black-autumn/why-the-ar-15-sucks-for-preppers
I'm not a fan of the charging handle or need for the forward assist. To me, it's a bandaid on a bandaid. Are there good things about the AR-15? Of course. The main one being separate lowers and uppers. Removable barrels is another. The fact it was adopted by the military is why it is prevalent. If something else had been adopted instead (like with a short-stroke piston) then I doubt anybody would go out of their way to buy an uncommon DI gun. Popularity doesn't make something de-facto the best. Would anyone go out of their way to buy an AK-47 if it was just a footnote on Forgotten Weapons?
AR-15's have been honed to almost perfection and are quite accurate.
True, they have. How long did that take now? I suppose when you have dozens of manufacturers trying to perfect a gun, you're bound to get some good results. That said, if those same companies put their efforts into some other XYZ gun, you'd achieve similar results. The same is true of a 1911. Is it a heck of a performer these days? Yeah, a $3000 one surely is. A mil-spec one? ehhh.. The design is old, and even the best of them don't like hollow points all the time. But let's face it, if the Legos box only allows you to build AR-15's, AK-47's and 1911's, you're gonna do it.
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I know some of these answers will ruffle some feathers, but that's okay. We all have opinions. I generally don't follow trends and buy what interests me. As the kids say, my "receipts" are I don't own a DI AR-15, but I do have a long-stroke PWS MK116. I don't own an AK variant, but I have a couple Vz.58's which I love. I do have a single 1911 though, and although I have shot a regular DI AR-15 and AK-47 before, I have no desire to own either.
)But it doesn't use STANAG or AK-47 magazines.
I understand why the first one is important to folks. The biggest reason is standardization and many different guns were created to use them, but the downside to that is not all guns have excellent compatibility with every manufacturer. At least with a proprietary gun with its own magazine, you're pretty much guaranteed it's going to work. 'Not always, but mostly. CZ has made some questionable OEM mags of late, but that's a rarity.
The AK-47 complaint however annoys me the most. So when looking at another 7.62x39 gun (like the Vz.58), people frequently complain it's not worth it because it is not compatible with one of the WORST aspects of an AK-47? AK mags suck. I said it. The fact a gun doesn't use them is a plus in my book. No BHO makes them very outdated. The also suffer from the same problem that QC is a crapshoot - not just because of magazine quality, but AK-47 quality. The same is true of any random 1911 gun and magazine.
The AR-15 is not proprietary. I like non-proprietary guns.
Isn't that true of most guns, especially pistols? So you don't own SIG's, Glocks, S&W, Ruger, bolt actions, shotguns? If you take this stance, you better only own AR-15's, AK-47s and 1911's.
Parts availability in an apocalypse.
Where exactly are you planning on buying parts in such a scenario? If you don't have spare parts on hand, then Brownells or MidwayUSA aren't going to be shipping. Gun stores will be closed or looted. If that's not the case, then you have a different definition of apocalypse or TEOT than me.
Secondly, if you think having an AR-15 is important because you can scrounge AR-15 parts off other people, that seems unlikely. If you come across a fallen comrade with an AR, just take his! It doesn't seem like repairing and piecing together guns is something we'd have time for.
If you mean parts availability because you personally own a dozen AR15's so that provides you with a built-in spare parts inventory? True, that does. But the same can be said of buying a dozen of any other gun too.
The company might go out of business, so how will you get parts?
This is frequently lobbed at AR-15 piston alternatives like PWS, POF, Adams Arms. True, but then isn't that also true of any company that isn't a maker of AR-15's, AK-47's and 1911's? At least with the AR-15 design (one of its best aspects) you can simply buy a different upper if that issue comes to pass. But this argument is basically true of any company. It can be said of a SCAR or ACR too. Let's not forget than even SIG has been known to abandon guns in favor of a new design and they're a BIG company. I've never had a problem with PWS. And I haven't even touched upon old, rare surplus guns. Nobody seems to have an issue buying those.
If AR-15's were meant to have pistons, they would have been designed that way.
If a piston variant AR-15 has a piston, then it was designed to have that piston. The question is a non-sequitur. How is that different than a SIG MCX or SCAR, or my PWS MK116? If it works, it works, In many cases it's an improvement. I mean, AR-15's weren't designed to have 7.5" barrels but companies manage that. Surely that should catch the same ire from purists? What about .300BO and all those other calibers that weren't designed for an AR? Aren't those abominations too? They also aren't great with suppressors but people modify their guns to handle that too - albeit with some powder blowback in the face. 'Doesn't seem like you should do that if it wasn't "designed" for it.
Direct impingement is fabulous.
Is it? Why doesn't anyone else (today) use it besides Stoner derived guns? Why do most of the new semi-auto rifles these days use piston? I know this is a common link that is pointed out, but he ain't wrong.
https://www.readyman.com/blogs/black-autumn/why-the-ar-15-sucks-for-preppers
I'm not a fan of the charging handle or need for the forward assist. To me, it's a bandaid on a bandaid. Are there good things about the AR-15? Of course. The main one being separate lowers and uppers. Removable barrels is another. The fact it was adopted by the military is why it is prevalent. If something else had been adopted instead (like with a short-stroke piston) then I doubt anybody would go out of their way to buy an uncommon DI gun. Popularity doesn't make something de-facto the best. Would anyone go out of their way to buy an AK-47 if it was just a footnote on Forgotten Weapons?
AR-15's have been honed to almost perfection and are quite accurate.
True, they have. How long did that take now? I suppose when you have dozens of manufacturers trying to perfect a gun, you're bound to get some good results. That said, if those same companies put their efforts into some other XYZ gun, you'd achieve similar results. The same is true of a 1911. Is it a heck of a performer these days? Yeah, a $3000 one surely is. A mil-spec one? ehhh.. The design is old, and even the best of them don't like hollow points all the time. But let's face it, if the Legos box only allows you to build AR-15's, AK-47's and 1911's, you're gonna do it.
------------
I know some of these answers will ruffle some feathers, but that's okay. We all have opinions. I generally don't follow trends and buy what interests me. As the kids say, my "receipts" are I don't own a DI AR-15, but I do have a long-stroke PWS MK116. I don't own an AK variant, but I have a couple Vz.58's which I love. I do have a single 1911 though, and although I have shot a regular DI AR-15 and AK-47 before, I have no desire to own either.
