https://www.smith-wesson.com/product/mp-15-sport-iii

Free-Float Handguard - Able to mount a multitude of aftermarket accessories.
Mid-length Gas System - Users can expect less felt recoil when shooting.
1:8 Twist 5R Rifled Barrel - 5R rifling profile has consistent contact with the projectile, ensuring a more accurate rifle. The 1:8" twist rate change allows for more variety of ammo to be used.

Priced at $799

Mid-length is easier on both the gun and the shooter. Nice.