I've been learning a lot about this topic lately. I got ahold of a Sinclair Concentricity Tool and also a Hornady (which I will be returning). I have measured quite a few cartridges for neck runout and bullet runout. I hear a lot of people saying .002" or .003" and under is true enough for long range shooting. Is this measured at the bullet tip? Loads I have measured (270 WSM), indicator near the bullet tip. Reloads, Norma Brass w/Accubonds: .001-.003 with an occasional .004" Reloads, Win Brass w/SSTs: .002-.006 with an occasional .008" Factory Rem Core-Lokt: Most around .006 with some up to .013" Federal Premium 140 Accubond: .007-.009 with an occasional .013" Winchester Supreme Ballistic Silvertip: About half .001-.003 and the rest .006-.014" I sorted the Norma reloads and shot 2 groups: One group with little runout and one group with .004" runout. The straighter ammo shot 4 into .475" with one flyer out at 1.2", and the 004" stuff shot a pretty random group at 1.25". When you guys get nice tight groups with factory ammo are you sorting it by concentricity? Are heavy barrels less affected by bullet runout? .013" is a ridiculous amount and probably explains why my groups with factory ammo have never been all that great. I would love to hear your experiences with this.