I have a Tactical Sollutions upper that I'm using with a Stag lower.
The good:
Yes, it's fun and very accurate. The stock trigger on the lower is about the only thing holding back it's accuracy.
It's very light, points well, and with the flat top you can put pretty much anything on it (I have the varmint version).
The bad:
Using a match trigger has been known to cause problems with these uppers.
I often get fail to fires. Especially with the 27 round mags. The 10 round mags are the way to go for reliability. Also I couldn't load 27 anyways since the springw were too tight.
Sometimes the brass gets caught while the action is cycling and pinches upwards into the ejector. This can be a real pain. Although this seems to be becoming less frequent as the upper gets worked in. As of now, most stoppages are a phase one and can be cleared with the tap rack method. I believe these are caused when the head of the round bends during feeding.
Which brings up another point. Use the copper plated ammo. The lead is too soft and gets damaged when being fed.
I had a rubber ring fall out of mine within the first 100 shots. I'm not sure if this was a buffer or what.
If you fire these uppers in a quick but controlled fashion then you won't have many problems. But... when you start firing too quickly the problems start up.
The mags:
They look good but are plastic. I've had two (that I know of) explosions/ruptured .22LR rounds in the breach of my upper. You get a jam and a small puff of smoke from the ejection port. No damage to the receiver/bolt etc. However the front feed lips of the mags were damaged. Often the damage causes the mag not to function. I have two mags with this now. One 10 rounder won't work anymore. The 27 rounder still works but has a nice chip in the front. If these were aluminum they would rock. I'm not a big fan right now of the plastic.
Summary:
A fun toy, I like it but like most semi auto rimfires you run into problems when going for high round capacity and or a high rate of fire.
