The pictured system incorporates the following to increase accuracy.
1. Timney Trigger #667s with 3 pound pull.
2. 18 inch barrel with free float tube and "Standard Length Gas System." Mid or standard length systems decrease recoil.
3. Magpul PRS (Precision Rifle/Sniper) Adjustable Stock.
4. Midwest Industry Flip-up Rear and Front Sight.
5. Harris 1A2-BRM Solid Base 6 - 9-Inch BiPod.
6. MAGPUL Battery Assist Device (B.A.D.).
7. BLACKHAWK AR-15 Ergonomic Grip.
8. 20rd MAGPUL magazine (not pictured).
If cost is a current concern, build out an additional upper or purchase a complete upper with at least a "Mid or Standard Length gas system and free float tube." You can always swap out the upper assembly with another AR's lower. Get started today, on any additional builds as parts and components are inexpensive.