Originally Posted by el matador
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.
I like to measure the bulletsshank/bearing surface if any is showing or down the ogive near the bearing surface. I have only received my Wilson concentricity gauge about a couple of years ago and it has helped me a lot in learning how to prep and size brass and seat bullets for concentric loads.
That said, I have not seen any noticeable difference between rounds showing .001 runout give or take to loads in the .008-009 range. Not saying concentric loads aren't any better than non-concentric, I just haven't seen the diff. I have shot a lot of sub 1/2 MOA groups with runout in the .005-.009 range.
A couple weeks ago I loded up 8 barrel accuracy test rounds for my new 6-284 before sending off for nitriding. 4 were in the .0005-.002 range and 4 were in the .005.-008 range. BTW, I had neck down the Lapua 6.4-284 brass to 6mm with a bushing die, nad that some times created neck runout. I had just cleaned the barrel so I thought I would shoot the 4 worse one first to sight in and foul the barrel. After shooting the first round, I adjusted the scope and shot the next three into a nice .4 group. This was just my mild break-in load and no accuracy development. I switched to a different target for the last 4 and the first of those landed in the same group area as the previous 3. The next 3 shifted left about and inch and printed about a .7 MOA verticla string for some reason making the total 4 group about 1 MOA for the "straighter" bullets. Maybe it was me? Moral of the story.... I think there are a lot of other factors that affect accuracy more than runout.
Now, when you have everything else dialed in, maybe good concentricity will get you a little more precision on the target. I'm guessing it helps the BR shooters.