Bullet runout

[Eagle Six]

As a newbie to precision shooting, I have a question.
If high runout does not interfere with accuracy, why do gunsmiths care so much about perfect alignment between the barrel and the chamber, to the point of using the indicator at the throat and a point forward, to guarantee perfect alignment between the first point of contact of the bullet and a section ahead?
Or are they different situations?

What is bullet "high runout"? How much eccentricity are you speaking of? I would say there are very few "perfect alignment" of chamber to bore. There are probably many that measure perfect within the tolerance of the tool used to measure. Closer to perfect when done by a reputable barrel manufacture or an accomplished gunsmith. Maybe not so much for high output production gun manufacturers, but still reasonably centered for the price and application. Alignment of chamber to bore is measured in much smaller degrees than what is commonly measured for bullet eccentricity/runout using rudimentary tools like the Sinclair Concentricity Gauge.

 

[liseo]

As I said, I'm new to this, but I'd like to understand, if you can help me.
When you have runout in the ammunition, the bullet is not perfectly aligned with the bore centerline.
And when the chamber is not aligned with the bore centerline, consequently the projectile will also be misaligned with the bore centerline.
So it seemed to me that the problem is the same, but with two different causes.

I'm probably wrong, and it's not the first time...

 

[Murray Brook]

I once read ,not sure where, that for target shooting (competition) try to get your run-out as close to zero as you can, for varmint and long range big game hunting .003 and big game under 500 yds .005. Seems to be reasonable.

 

[Eagle Six]

As I said, I'm new to this, but I'd like to understand, if you can help me.
When you have runout in the ammunition, the bullet is not perfectly aligned with the bore centerline.
And when the chamber is not aligned with the bore centerline, consequently the projectile will also be misaligned with the bore centerline.
So it seemed to me that the problem is the same, but with two different causes.

I'm probably wrong, and it's not the first time...

I'm not sure I can help you, and being new isn't an excuse for questioning things. Some ole guys that been doing this for decades question everything, I'm one of them.

If your case is concentric, and the bullet is seated concentric, and the chamber is concentric with the bore, and the bore is concentric and the bolt face is square with the case base it would seem to me I would get good results as opposed to all those parts and pieces being catawampus with each other.

So being perfect is I suppose better, but I question how much better and can I prove it, or is the effort worth it. I suppose a lot depends on how much any of those are out of spec of being perfect.

My case necks are less than .001" eccentric and my bullets seats are within .002" of concentricity. I have no idea the straightness or center of my chamber as lined up with the bore and I get .2X - .3X MOA groups. I have met my required goal. I have found that interference fit effects my precision more than nominal bullet runout. Also have found that the friction off inside neck to bullet inconsistency effect my precision more than nominal bullet runout. All of this in a deep throat chamber that probably shouldn't shoot as precise as it does.

It would make sense the better we are making precise shit, the more precise that shit will be! I find it more difficult to control precision with the nut behind the trigger, than precision with the nut behind the loading press. Just my Redneck humor!!