It's a .22 Grendel / .224 Predator. Reamer specs allow for 40 thousandths more freebore for heavier projectiles and Hornady's new 62 grain Varmint Target projectile. Hornady is recommending a 1:7" twist for the same reasons.
Lots of folks have been shooting it for years. We shoot light projectiles in our 1:8" twist ARs (we have 8 barrels in builds right now). We are starting with 53 grain, going up to 69 grain.