Slimjim thanks for the summery (Good read). Looks like I'll stick with what I have. It's hard to improve 1 5/8" three shot groups at 200 yards with a hunting rifle.

Could you post a photo of the screw and cartridge?

Last night was all .270 bullets. This morning I loaded up ten .223 cases with 75gr A-Max bullets and repeated the concentricity test.

- First, the .223 looked right at home in this tool and the offset screw that pushes the bullet looked appropriately sized as opposed to what it looks like trying to push a larger .270 bullet.
- There was significant differences in the run-out reading of the V-block compared to the Hornday tool as you can see below. I believe this is due to case imperfections and saw dimples for AR ejections on the cases that read large amounts of run-out with the V-Block.
- Adjusting run-out to 0.001 or less was a snap.

My impression of this tool is much more positive this morning and I trust its readings. I'll take these bullets to the range this morning and see how they shoot.

Bushmaster wrote:

Could you post a photo of the screw and cartridge?

Bushy, I have to head to the range right now to get there by sunrise. I'll post some pictures when I return.

Just got back from the range. No improvement in group size, however, I haven't shot my 75gr A-Max load enough to make any definitive conclusion. Here are some pictures of the tools.

Here is a composite showing the size of a .223 compared to the .270 Win.

Slim

Last year after my buddy bought the Hornady case concentricity gauge, we did a test. He came over to my house and we loaded up 20 338 lapua rounds and checked them with his Hornady gauge and they were straight to .002. Upon chambering all 20 rounds outside, than extracting the live rounds we found that the concentricity went out of wack with his custom built rifle!!

After chambering 20 live rounds (outside) and than extracting it (never fired) and than chucking that same round back into his Hornady tool, it was off by .004", and this is a rifle that custom built and cost almost $9,000. But yet his rifle shoots moa at 600 yards no problem.

We were both surprised at the findings of this test but in my opinion, if you seat the bullet close to the lands on the rifle, you will get good accuracy, on the other hand, seating the bullets back with normal loads might not get so good accuracy, it depends on the gun's leade.

OV1, after the rounds were cycled through, did they still shoot MOA with the increased eccentricity?

Ok, Bushy, I did these pictures just for you!

slimjim wrote:

OV1, after the rounds were cycled through, did they still shoot MOA with the increased eccentricity?

There was no increase or decrease in his shooting groups with the Hornady tool compared to just loading the bullet normally. We both came up with the conclusion that even if you were to get concentricity down to .001" or better, when you go to chamber the round, the bullet, case will conform to the chambers dimensions making all concentricity adjustments done with any tool null.

Try the same thing we did and see if you get the same results.

Omin, this is one of the best remarks I've read in this thread. I was already wondering how the oldtimers with their 45/70 could hit their target at more than 1000 yards without all these equipment (using iron sights?).

SJ, do you already put a mark on all your cases so that you put them in the chamber at exact the same position as the previous time? Now you measure the bullet's concentricity, but what about the case?
Think about a lathe. When your piece is not clamped as required, you still can turn a part exactly round, but when you should measure concentricity over the total piece, so also the part that's in the clamp, I think it could amaze you.

Ominivision1 wrote:

Try the same thing we did and see if you get the same results.

OV1, I did sort my rounds by concentricity and ran tests with those 0.003 or below and those that were 0.005 and above. I did see a measurable difference in average velocity, velocity spread, and group size.

I think concentricity is important. I'm beginning to think it is an exponential problem. Within a small range near zero, concentricity doesn't have much of an impact. As the cartridge/bullet becomes more out of round, the more significant the affect. Stay within the lower range and its difficult to measure the impact.

Aloysius wrote:

SJ, do you already put a mark on all your cases so that you put them in the chamber at exact the same position as the previous time? Now you measure the bullet's concentricity, but what about the case?

Aloys, I clock my .45/70 brass and load it into the single-shot breech the same every time. This is not something I do for my bolt action or semi-auto rifles.

I've been measuring the concentricity of the brass case and necks before I load the bullet so I can measure the affect of the loading die. I've found that the brass is concentric, perfectly concentric, coming out of my Lee Classic Hand Die and my standard Redding Dies before the button is pulled up through the neck. My more expensive Redding S-type Die isn't as concentric (0.001 to 0.003 off). Pulling the button back up through the neck on the standard die causes run out so the advantage of the S-type die is it doesn't work-harden the brass as much. Having a bullet seating die that holds the case and bullet in alignment prior to seating seems to be an important step in the process of loading the most concentric rounds.

This morning I realized that the $25 Lee Hand die has a more sophisticated neck forming technique in that it tapers the neck instead of making it one consistent diameter. This may also be why my bullets load straighter in cases run through the Lee Die similar to how Redding recommends to only size 1/2 the neck to improve concentricity.

Nice pictures and interesting thread. Have you measured the neck without a bullet seated? I see a lot of points of possible error in the Hornady tool and perhaps less in the other. I would measure several points on the full case to proof the centering of the case. If the measurement of roundness is out greater at 1/4 inch from the neck than 1/4 inch from the base then suspect the case isn't centered in the chuck. Do not assume that the case itself is perfectly round. This can also be checked once you have proved the case properly centered. Others have mentioned variations in neck thickness. The bullet center when seating will conform to the neck center unless the neck opening is really off center. There is enough give in the brass and within the seating die to allow this conformation to take place. However the seated round will not be centered with the case base if the center of the neck is out.

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? I have read lots of anecdotal on this issue but never really read anything conclusive.

Just one other point if I may. I just sized 500 brand new Starline Brass cases in 45 colt in a carbide die. Based upon the feel of the press I am confident that there was a slight variation in the circumference of the cases or the case wall was not exactly perpendicular to the base in all cases or both. Perfection is hard to get and maintain from the manufacturing process for case and bullet to the reloading equipment to the fit of the rifle components. All may have errors that affect the centering of the axis of the bullet to the rifle bore's axis. The pursuit of perfection can be fun and fulfilling but often frustrating and expensive.

Guess that is my $2.22 worth :-)

Check this out. ---> www.theboxotruth.com/docs/bot50.htm

Thanks Slimjim...I believe everyone should be thanking you for this thread. Very well done and very informative too.

Omni raised an interesting thought. I may have to look into it. That is: Does concentricity change when chambered. I know that in both my Winchester M94 and the Browning A-bolt the round gets banged around a bit when leaving the magazine and entering the chamber.

Makes you wonder if for us regular guys it might be a waste of time and money if they are going to be knocked out of round anyway.