I purchased Ruger GSR about a year or so ago and it has become my most used 308 caliber rifle.
It is light, fast handling and carries well in the field and has sufficient magazine capacity to deal with most hunting and social situations that arise in the field (I live and hunt about 10 miles from the Mexican Border).
With regards to sighting systems, I have used the factory supplied adjustable sights, forward mounted Burris Fast Fire, a Weaver 2X handgun scope and conventionally (rear) mounted rifle scopes and all have worked well for me.
It is accurate with any decent ammo and it will turn in groups of less than an inch if I do my part.
I find that I get the best accuracy with bullets of 165 grains and heavier and groups tighten considerably with my handloads when the bullets are seated out to match the length of the magazine.
A lot of people ask whether they should buy the Ruger GSR or the Springfiled Armory Scout version of the M1A and to me it is an apples to oranges comparison.
That said as an owner of both platforms, who has hunted with both I will share the following:
Out of the box, the Ruger GSR blows the M1A away with respect to accuracy, ease of handling, weight distribution, trigger pull and will handle any 308/7.62X51 caliber ammo you can find with no need to defer to a gas system.
The Ruger Scout can be conventionally scoped without the use of secondary mounting system and when conventionally scoped it lends itself to a conventional cheek weld that requires no strange placement of the head/face or secondary cheek pad to administrate.
The barrel is factory threaded for use of a suppressor (if your so inclined) so there is no need to spend an additional 250 bucks for 5/8X24 suppressor interface and an adustable gas plug to get it to run with a Silencer in place.
With regards to cost, for the the price of an M1A Scout I can buy a Ruger GSR and 600-800 rounds of Federal Gold Medal Match, shoot for 6 or 8 months and have a pile of quality brass left over for reloading.
To me, the only advantage the M1A has over the GSR is magazine capacity and sustained rate of fire.
Now, I'm not bashing the M1A (I have 3, the SOCOM II, the Scout and the full sized loaded model with Stainless BBL) and appreciate the platform as much as anybody else but having spent days carrying both in the field, the Ruger GSR suits me and my needs a whole lot better.
M1A pics to appease those so oriented
About the only thing that I would change on my Ruger GSR would be the addition of a tactical bolt knob. I find that the factory bolt knob small and easy to miss when running the bolt from the shoulder.
I am by no means stating that the Ruger GSR is "The Perfect Rifle" but for me it covers a whole lot of bases in one package for a reasonable price.