The AR platform is as accurate as you make it. From what I understand the SR556 is a very accurate rifle, but as with any rifle, you have to find the ammo it likes. Some like 55gr, others 62gr etc. From what I have read, you can swap the barrel, but it is a pain with the way they have the transfer pin and handguards affixed. The handguards are proprietary, again from what I have read, and that means that you can't swap them out for any other piston compatible setup if you don't like the Troy handguards. Also, I see that the bolt carrier leaves the firing pin un-shrouded. That is a no-no because then the firing pin is much more likely to break from cycling against the hammer.
My opinion, if you are going for a varmint rifle, I would go with an 18" Mid-length gas system in a heavier profile barrel and assemble it yourself, or purchase the lower and upper separately. This way, you can at least get an upper that you want (or as close to it as you want). I would check out this barrel...
Blackhole Weaponry AR-15 18" Mid-Length Stainless Steel 5.56 1:8 Poly Barrel - Surplus Ammo
I have a 16" version of it and it is very accurate. The twist rate allows for greater variety of bullet weights to be used and it comes with a free upper. Plus assembling yourself makes it possible to really get to know your rifle. You can always buy an assembled lower and just build the upper too.
Or, if you want to stay 16" check this out.
Surplus Ammo & Arms Match Stainless Steel 16" 1:8 Polygonal Mid-Length HBAR Blackhole Barrel AR-15 Upper Recevier - NO BCG, CH, HG - 5.56 - Surplus Ammo
Here is another website that has terrific quality and excellent customer service. I have one of their 7.62x39 barrels and can shoot one ragged hole at 100yds all day.
SkeletAR -5.56 -16""
In my opinion, you can get just as good of quality or a better quality AR for what you will pay for the SR556. You just need to do some homework. There are also lots of videos on youtube from midway and Brownells on how to build an AR, so it is very easy to follow for a beginner. A few simple tools is all you need. Plus you get to know your rifle and have the tools to change or fix things when you need to. There are lots of options with the AR. That is a blessing and a curse. You can't have just one AR.
I hope this didn't confuse you too much and helped you out.
