The XCR defines "mediocre".
Having recently owned one and comparing it to other non-restricted and restricted rifles in it's caliber, I would agree with koalorka.
It shot ok (comparable to any lower end stock AR) but there were a number of small/large design features and quirks that I found disagreeable for a $2k plus rifle.
I'll elaborate before any of you die hard XCR fans jump all over me for talking ill of your prized possession.
The first thing I noticed when I picked it up was the front end weight. Rob Arm chose to make our 18.5 inch barrel in an HBAR profile which directly contributes to the front heavy feeling. As soon as you add a light and a vert grip you really do notice it if you are used to shooting ARs.
The second thing I really wanted to check out was the gas system and quick change barrel feature. I immediately noticed the looseness of the gas tube...not just a little wiggle room but loose to the point where the tube could move back and forth substantially. It left me feeling like I'd assembled it all wrong and something wasn't lining up. Upon further reading online, I discovered this movement was "normal", Engineered there from the manufacturer to aid in the shaking loose of carbon fouling. Some people had taken to smooshing the tube slightly to get rid of the rattle. Not what I want to do to an expensive rifle. If you're like me and used to Swiss Arms and ARs then this might drive you nuts, cause it bothered the Sh*t out of me...but I have problems
The quick change barrel feature definitely did not impress me. There are no guides or rails to index off of in the receiver but instead there is a bolt on the bottom that acts like a set screw and holds the barrel in place. Not only did it leave me feeling unsure of the alignment of the barrel but also how secure it was. The last thing I would want is the barrel to shake loose during firing. It never did...but hell I didn't abuse the crap out of it.
There are also a number of other bolts (Ejector, Casing Deflector etc.) that should be checked and possibly loc-tited in place. Kindof annoying. Really disliked the delrine cocking handle and casing deflector. The didn't break but felt cheap.
The front pivot pin is retained by a small spring clip which was all backwards when I received the rifle. This puzzled me for a moment on why I could not slide this pin open...but I figured it out! Using this type of containment method for the pin is the cheap way to go. If you were to loose this small little clip, which is just hangin in there by the way...not like a C clip for the 180B, you'd be pooched in the field.
Someone can correct me if I'm wrong, but this rifle was entered into competition for a replacement combat rifle no? From a military end users perspective, I'd be mighty disappointed to give up a Colt for this. Definately NOT something I'd take with me into harms way.
So if you are just looking for a plinking, cool looking, gravel pit rifle, then this might be the ticket for you. BUT I can honestly say, there is much better designs out there on the market that have been adopted by governments and proven over the years. I took a chance with the XCR, despite Rob Arms crappy QC track record and like koalorka said it's mediocre.
The one thing I'll give Rob Arm is they do have outstanding customer service and are willing to go the extra mile for our horrible little gun market....which cannot be said of most other US companies.