I realize I'm opening Pandora' box , but here it goes. How often do you check concentricity on your bullets? I'm looking at trying to improve my group. I know that seating the bullet is very important and contributes too this as well. From what I'm reading there are pros and con to this .Am I wasting my time?

When I was shooting 1k BR I checked every round for concentricity. Anything with more than .002 runout (not many) were used as sighters, and anything over .003 (VERY few) was used for foulers.

A way to see if your rifle cares is to check a batch of loaded ammo and mark the rim at the high (or low) spot on each round. Fire several groups with the marked spot in the same position in the chamber. If the rifle groups better with the 'oriented' ammo then worrying about this might be worth it.
C.G.B.

quote:

Originally posted by john post:
I realize I'm opening Pandora' box , but here it goes. How often do you check concentricity on your bullets? I'm looking at trying to improve my group. I know that seating the bullet is very important and contributes too this as well. From what I'm reading there are pros and con to this .Am I wasting my time?

I take your post as asking about the projectile concentricity not runout on a loaded round. I would think that even a slightly out of round bullet will be swaged to bore dimensions on it's travel. In cup and core or bonded bullets you have the core to jacket interface to worry about. The bullet could be completely uniform on the outside but have an off center core. You'd never know. With solid copper or bronze bullets you could measure for roundness and segregate that way. I have rolled bullets on a piece of plate glass while watching and listening. Perfect or near so bullets will roll smoothly with a consistent pitch noise. Off center cup and core or bonded bullets roll unevenly and may even rock back. You can see this and the pitch varies. It is also a good quick check for loaded round run out. There is an old Hornady film that demonstrates the difference in accuracy between bullets that were slightly out of spec and those that met spec. The groups opened up about an inch. So the answer is yes, it does make a difference. Sticking to premium target or varmint bullets should mitigate it though.

Bobster, Benchrest guru Tony Boyer agrees with you regarding the bullet swaging (aligning) into the bore. I did a study some time back using a bunch of factory Remington .223's. Bottom line was that runout (concentricity) made little difference in accuracy. Extremes showed the smallest runout made the largest groups and, conversely, the largest runouts made the smallest groups. Go figure.