I remember one that disappointed me. Rhineland Arms R22.
You might have never heard of it. It was a short-lived new .22LR rifle that appeared about 2005 or so. It used common AR fire-contol parts and a 10/22 bolt and magazine system in an H&K-looking frame. I got on it early and mine has a two-digit serial number.
It wouldn't work right out of the box. Wouldn't feed about one out of every three or four rounds from any magazine, Ruger or aftermarket. When it DID fire, though, it was stunningly accurate, and would put most of my .22 bolt actions to shame.
I diagnosed the problem and remember having to do some careful filing somewhere in the receiver or mag seating area, and it worked better after that, but I never got it to 100% function before I lost interest in it. Got down to maybe one or two malfs in a 25-round mag. I also remember having to file the extractor to a much sharper hook shape to get reliable ejection--the chamber seemed to be tight, which is great for accuracy, slightly less so for function.
Two other things I didn't like about it: The buttstock was, I believe, sourced from airsoft stocks, and is very light and feels and sounds cheap. Also, I really wanted to set it up with HK-type iron sights. Never could find any. The thing has a full-length rail so anything that will bolt on an AR will bolt right on, but all AR-type sights I've ever seen are set up for a high sight line a la the original AR/M16, and I wanted much lower sights for a better cheek weld.
I eventually (three or four years ago) ran across a set of satisfactory sights on the CZ website, intended for one of their carbines. They're not exactly like I wanted, but they ARE exactly WHERE I wanted them to be, and they were very reasonably priced. Also a few years ago I lucked into a surplus HK buttstock, satisfyingly sturdy and weighty. It should have been a direct bolt-on, and ALMOST is, but there's a little interference somewhere that will require a little careful grinding on either the lower receiver (which would be easy) or on the stock (which would be more difficult). I haven't gotten around to this little project yet.
Here's an old pic of it with a scope, along with my DPMS M4 .22LR, which is also VERY accurate, and reliable.
