I read the posts here and I worry that some will get the idea that if they get a RRA 9mm upper or a .22 conversion or some dedicated upper that they are opening up cans of worms with nothing but troubles.

This is not so. Like many here I have put together a variety of AR's. After all, one is never enough! I have the standard M4 style in .223, a couple of Middies, a 24in Bull Barreled Varmint model, a 9mm, and a .22 conversions.
They all work PERFECT. They don't do anything bad, I would trust my life to any of them. All but one I put together myself. I did use all good parts: Double Star, Rock River, CMMG, Spikes, M & A, Cavalry Arms, etc.. The "name brand" vendors you see here normally put out quality products. If you stick with the good ones and educate yourself on how to do things you have a good chance that all will go fine.

Problem is you usually only hear about the minority of projects that have problems. This gives a false sense that "everyone" is having trouble.  Well, that just isn't how it is. I would bet that if you did a poll you would find that the vast majority of people have few problems that are anything more than simple. I just hate to see people avoid trying a 9mm or .22 conversion if they are so afraid of having endless trouble with them.

So, have faith. The 9mm and .22 ARs are loads of fun. They have their place and you might just like them. I know I love all of mine. The .22 is cheap fun. The 9mm is a good "in between" rifle that works great for closer ranges. It has lower recoil, less noise, and is much easier to reload for. For some its the fact they can use them at most any indoor range that makes a difference. Also, those nice heavy pistol bullets hit hard and let you know something is happening out there.  The .22 guns are a nice low-cost way to gets lots of quality range time for a little money. Ammo costs do add up and a lot of folks are finding .22 keeps them shooting for an affordable price.

Don't think that these guns are a headache, it just isn't so. You are hearing about the few that have problems. Most of these problems get ironed out in short order with simple fixes.

Essentially any weapon can have a problem (except a 1911, I hear...).

The cause of the problem(s)...that's the issue. Design? Use? Maintenance? Ammo? Mags? Fouling?

The list goes on....some are more prone to fail then others. But all machines fail.

Hey, I have seen a few 1911's that just didn't work. Big name ones at that. Like you say, any machine can break or malfunction.

Double tap....sorry

I had a Kimber TLE II that would not eject properly, and it was brand new....after doing some research...found out the extractor needed to be tuned....So any weapon can give ya problems....you just gotta find out the tricks to cure em...I had a 9mm AR with tons of probs, till I tuned the ejector....My 7.5" Model 1 Sales dedicated .22 AR15 on the other hand has run beautifully!!

Now Glocks....ur not gonna find one of those that doesnt run right!!!

My model 1 .22 runs on anything I feed it, but my Spikes will not get through a mag without a failure, it needs some tuning I guess. My Oly 9mm has never failed........It comes down to "shit happens" sometimes.

The deal with the conversions is that they may require some tweaking to get them to run right.  Don’t forget that there are a lot of variables with mags, blocks, uppers, bolts, hammers, ammo, etc.  Not every combination is going to run out of the box…

My 9mm build required tuning the ejector and removing material from magazine followers.  A different type of magazine ran fine without modifications.  Yet another magazine caused constant problems and had to be returned…

My .22 conversion was merely a matter of trying different types of ammo to see what would feed reliably…

I don't know what is wrong with your 9MM and .22LR ar's,

But what ever it is, it has to be bad if they are working just fine.

Tell you what, you ship them to me, and I'll shoot the snot out of them until they are unreliable pieces of junk and then I'll send them back to you.

I won't even charge you for my services, but I do have a full time job so it may take a while if they are real reliable.