Good point Bushy regarding the old jack handle. I would venture to say the concentricity would probably get knocked out of wack when loading a round from tube to chamber. I know for sure on both my older M700 they get reset to my guns chamber size.

I'm thinking If you are loading for a benchrest tolerance chamber and seating the bullet to any amount of touching the rifling in the leade the bullet will straighten itself when chambered. This is not to say that a lot of run-out of the seated bullet is acceptable.

Another thought that should be important in accuracy, is even weight distribution across the diameter of the bullet; i.e., the bullet must be in balance. Most good brands have this licked, but this could be a factor in cheaper bullets. Much bullet run-out in normal reloading dies is caused by the expander as it comes back through the neck. Benchrest sizing dies do not use an expander as far as I know.

MacD wrote:

Have you measured the neck without a bullet seated?

Yes, before I loaded every case to help understand what was going on. If there was any run-out in the neck prior to bullet insertion, run-out would always be greater after the bullet was seated. Of course, this is partially true because the way the v-block measures run-out, the measurement is taken further from the source causing the error. I did find that the variation in run-out was greater when seating the bullet with the standard Redding Die that did not hold the bullet and the case in alignment prior to bullet insertion.

MacD wrote:

Others have mentioned variations in neck thickness.

My reloading buddy advised me to check this and throw out any case that had neck thickness variation greater than 0.0010 to 0.0015. E.g., a case that varied between 0.0128 and 0.0139 was kept. One that varied from 0.0125 to 0.0148 was tossed. New brass is pretty consistent but there are a few that don't meet this criteria. Neck thickness variation increases with each firing. I must have tossed about 15 cases or half the cases I was reloading at the time.

MacD wrote:

Once the round is chambered I don't see how it can move through the barrel not centered. How would a small error in the centering of the bullet in the case change this?

This is my theory. The neck of the chamber is several thousands of an inch bigger than than the loaded case. You can tell that by measuring your fired brass. My loaded brass is 0.302 and my fired brass has a neck size of 0.309. Thus the bullet is suspended in the chamber by the case and must enter the bore through the forcing cone. If the bullet is concentric, it smoothly enters without causing fluctuation in chamber pressure. If the bullet is really out of alignment, I wouldn't be surprised if the bullet is deformed slightly since its much softer than the barrel, especially at those pressures. I noticed a measurable reduction in velocity when shooting bullets that were 0.005 to 0.010 out of round - 75 fps.

Ominivision1 wrote:

I would venture to say the concentricity would probably get knocked out of wack when loading a round from tube to chamber.

From the product reviews I've read, users have been unable to "adjust" the concentricity of factory crimped bullets. It was also my similar experience that concentricity could not be changed with the Barnes Banded Bullets.

Aloysius wrote:

Now you measure the bullet's concentricity, but what about the case? Think about a lathe.

MacD wrote:

I would measure several points on the full case to proof the centering of the case.

Well, I kept thinking about what you two said and went back and took concentricity measurements all along the case. The cartridge settles in very snug in the Hornady set-up and you can't move case off center. However, it turns out that the rod holding the base of the cartridge is on the rim not the thickest part of the case. I did find some rims that were 0.005 off center measured on both the .270 and .223 cases. Though someone could argue that this dimension isn't critical because your measuring run-out at the other end (where the bullet is), it does introduce at least 0.001 of error right off the start if the case rim is not centric.

I keep feeling like I'm taking one step forward then two steps back.

In summary, I do believe I understand more today than I did two weeks ago. If you followed some of my other posts, I had switched from my $25 Lee Classic Handloader Dies to standard Redding dies with a RCBS Rockchucker press -- and my group size on my .270 Win increased and my velocities dropped with greater variation. When I consulted a hunting buddy of mine with more experience, the first thing he said was "I bet concentricity is your problem." He headed over to my house with his measuring tools and, sure enough, many of my bullets were out of round, some as much as 0.010. I took the steps he told me to do to improve my situation and my groups have returned back to 1/2 MOA. I also verified that cartridges that were 0.005 out of round or more gave me the poor performance I was seeing when I changed my reloading set-up. I believe the two most important steps I took were; 1) I got rid of cases with neck thickness variation greater than 0.0015, 2) I changed to a Redding bullet seating die that aligns the case with the bullet prior to insertion similar to the Wilson and Forrester Dies he uses.

And, your forum suggestions helped a bunch, too. Thanks!

slimjim wrote:

I keep feeling like I'm taking one step forward then two steps back. And, your forum suggestions helped a bunch, too. Thanks!

Slim, are you kidding me?, your post has been very informational to everyone here on the NUT If it wasn't for your post in the place, none of us here on the NUT would have known. While I was always skeptical, your post got me off my butt to do some checking on this. I did call up my shooting buddy that has the Hornady tools and a few others , and hopefully this coming Wednesday we will test the 30/30 jack handle.

I think Bushy is right about this tool for us regular guys.

Slim:
This was a very interesting post for me also. Thanks for sharing your experiments with us. It definitely got my gray matter warm.

Same here Slimbo, except mine's not gray, more cinnamon I think. I'm not a competition shooter (only with myself) but any little tidbits or methods do get you thinking outside the box of ordinary and paying attention to the little details that might otherwise be looked over.

Thanks Slim
Suz

Always nice to think and talk about such things, they can make you very clever at the end. I'm testing already for more than 30 years and still going on. But my eyes helped me make the choise not to try for big distances anymore, which does not make life and shooting easier, but it sure helps to make reloading easier. Why bother for your groupe at 600 yards when you could only see 200 yards? When your own faults start being bigger than improvements in your loads, priority changes. Which doesn't mean it's not fun to talk about it.
When you get old enough I've been told that there are a lot of things you cannot do anymore, but as long as you can talk about them, they still can bring you joy

just imagine how much the lee enfields push the .303 round out of alignment when they get crashed into the chamber up that ramp that get lead smears on it!!!!

slimjim wrote:

However, it turns out that the rod holding the base of the cartridge is 0.005 off center measured on both the .270 and .223 cases.

This statement is inaccurate. The tool is not off by 0.005 it was the case rims to the sides of the cases. The couple cases I used were identical. I should have tested more cartridges. This tool was easy to use and adjust the .223 cases and, since I've become a believer in concentricity, I'm going to keep it and use it to continue with my learning.

SJ, it's even inaccurate to discribe this as my quote. I usually don't play with these inch-numbers as I'm used to think in mm

and I also believe in concentricity. I think Barnes has bullets made on a hydraulic press and others on a CNC-lathe. Maybe you should once compare these two... and I mean the bullet before reloading.

Sorry, Aloys. I updated the post and corrected another one of my errors.

slim heres a test for you. load up your magazine and fire all but one round then check the last round out if your .270 is anything like mine that lovely soft lead tip will be mashed!!! I used to get this problem alot when shooting wallabies with the big gun as I would often top up the mag 3 or 4 times before firing the last round at a fleeing Aussie over stayer. the nosler ballistic tips got stuck in the mag to stop this problem till I shot holes in the hillside with them too!!!

Elvis, my Tikka is a 3-shot thermo-plastic magazine. The ejector port is small so I almost always shot a loaded magazine. However, I only use ballistic tips for my .270, not softpoints. I've not had this type of problem.

Returned from another range session where the .270 Win is shooting well. Yesterday I was using the 3rd mil-dot to shwack gallon milk jugs full of water at 500 yards.

I have refined my concentricity check process. I now roll the loaded cases on the kitchen counter-top and pick out any that have a wobble in the bullet tip. This is quick and easy to do. Then I place them in the Hornady Concentricty Tool and correct them to be true (at least for the .223 rounds).