Concentricity .. how important?

[Lonewolf74]

is it time to swap out my highschool aged Lyman orange crusher for a Forster coax press?

I'm strongly thinking about going this same route myself.

JE is the Co-ax the press you are looking at as well?

 

[bigedp51]

Full length resizing reduces the effects of neck/bullet runout. The full length resized case body and neck do not touch the chamber walls. The case is supported in the rear by the bolt face and by the bullet in the throat.

NOTE, at the Whidden custom die website they tell you they get the most concentric resized cases with non-bushing full length dies.

Below German Salazar from the Rifleman Journal website. He is answering a question about partial full length resizing. And explaining the benefits of full length resizing and bullet runout.

Reloading: Partial Neck Sizing
by German A. Salazar
http://riflemansjournal.blogspot.com/2010/06/reloading-partial-neck-sizing.html

"Now the last scenario, a full-length sized case in which the neck is also fully sized. There is clearance at the neck and in the body of the case, the closest fit anywhere is the bullet in the throat. If the neck to bullet concentricity is good (although it needn't be perfect), then the bullet will find good alignment in the throat and the case body and neck will have minimal influence. Let's not forget that the base of the case is supported by the bolt face or the extractor to a certain degree as well; this is yet another influence on alignment. As you can see, there are several points from base to bullet that can have an effect. My procedure is to minimize the influence of those that I can control, namely the case body and neck, and let the alignment be dictated by the fit of the bullet in the throat and to some extent by the bolt's support of the base. Barring a seriously out of square case head, I don't think the bolt can have a negative effect on alignment, only a slightly positive effect from minimizing "case droop" in the chamber. Given that a resized case will usually have a maximum of 0.001" diametrical clearance at the web, this isn't much of a factor anyway."

I have the two runout gauges in the photo below a Hornady and RCBS concentricity gauges. The Red Hornady gauge holds the bullet like if it had been full length resized. Meaning holding the base of the case in the rear and by the bullet.

The RCBS gauge spins the case on its body and is more applicable for cases that are neck sized only. Meaning the case body will have more of a guiding effect on the bullet in the throat.

Click on the image below to enlarge by Kevin Thomas of Team Lapua USA, and read about the rat turd in the violin case.

Bottom line, the U.S. Military considers match grade ammo to have .003 or less bullet runout.

 

[J E Custom]

is it time to swap out my highschool aged Lyman orange crusher for a Forster coax press?

That's the one I was looking at. But I cant find any that is in stock anywhere.
+ they are expensive.

J E CUSTOM

 

[orch]

I ended up going the Forster coax route, worth every penny, made a huge difference in concentricity....


JE, X-reload.com up here in Canada shows them in stock... they are pricy but you'd be paying around 70 cents on our Canadian copecks....

 

[J E Custom]

Thanks everyone, I found one and it is on it's way. For those that dont or cant buy something with these features, I found that removing the shell holder clip that holds the shell holder in the ram allowed the shell holder to align itself a lot better. So maybe the new press will shave off some more Inconsistencies.

Probably Everyone has an acceptable level of precision. But mine is zero run out. I still believe that if I could load ammo that The brass fit the chamber perfically, the neck was perfically centered on the bore centerline. And the bullet was concentric and also centered on the bore centerline this would be the most accurate. How that is achieved is a different story and is done different ways and in different opinions.

It would be perfectly concentric to the barrel bore and would/should launch the bullet perfectly (I know that is hard to achieve, but what's wrong with trying). I accept nothing that can be improved.

The only thing that i can be sure about is that the best accuracy and consistency is with ammo that is perfectly concentric to the bore and has no concentricity issues (.0000 concentricity).

J E CUSTOM

 

[rockwind]

It's been a while since i did a concentricity test but I will try to remember the results as best i can.

I loaded 40 rounds with the same components and shot them in the same rifle. This load was my accuracy load for my 7/08 that will consistently shoot 1/10 tenth moa groups.

After loading, I measured all rounds for concentricity and sorted in this order.
Zero runout.
.001 thousandths.
.002 thousandths.
.003 thousandths
.004 thousandths
and over .004.

All rounds over .004 were straightened and sorted in this order
Zero runout.
.001 thousandths
None of the straightened cartridges were over .001 after straightening.

Obviously, the zero runout as loaded were the best.
.001 to .002 showded very little accuracy loss over the zero runout loads @ 100 yards. 200 yards you "could" see a slight difference
The greater the runout the worse the accuracy.

During this test it became obvious that any ammo loaded with greater than .003 thousandths of runout was unexceptable for someone that strived for accuracy.

Oddly, any load that had been straightened, even though they had zero runout did not shoot as well as those loaded with zero runout. and the ones with greater than zero runout shot about as good as the .003+loaded ones.

So I came to the conclusion that the more concentric your ammo is the more accuracy you will have. The chamber, the bullets and cartridges/ammo shoots best if it is concentric to the barrel bore.
depending on the shooters skills, concentricity may not be a factor at 1 to 200 yards but beyond that It does make a difference.

J E CUSTOM

JEC,,,,OR ANYONE,,,,, in your quest for concentricity, what have you found to be some of the most important things to do? i use redding fl bushing dies on a redding t7 press, i float the shell holders and have tried other tricks but i gotta say, the concentricity is not that impressive,,,,from .0005 to .007, average is .003-.004. weird

 

[J E Custom]

JEC,,,,OR ANYONE,,,,, in your quest for concentricity, what have you found to be some of the most important things to do? i use redding fl bushing dies on a redding t7 press, i float the shell holders and have tried other tricks but i gotta say, the concentricity is not that impressive,,,,from .0005 to .007, average is .003-.004. weird

I will take a shot at what the problem may be.

First the full length die starts to size the case body before it is all the way down on the fired case. and if the case is not of uniform thickness (And they rarely are) It will size the thin side first misaligning the case to neck OD. The chamber centers the OD of the case body and the neck. and If you turned the necks to a uniform thickness the ID of the neck will/should be centered/aligned to the bore.

I get the best results using a/the Competition bushing neck sizer because of the sleeve that holds the OD of the case body without sizing it and possibly moving the body out of alignment from the chamber.
Then the bushing can/will size the neck centered because it has a little float.

A common mistake made with the bushing dies is to leave the expander ball in the die. Proper bushing size eliminates this and only sizes once per operation. Bushings should be .001 to .002 thousandths smaller than the loaded cartridge. To much bullet grip can skue the bullet when it starts to be seated. Also be sure and de bur all case mouths to aid bullet seating.

I turn "All" necks to uniform them before the first firing, to assure the case neck is concentric after firing the first time. the case body may not be concentric on the inside, But the Outside of the case body Is and the case neck will be concentric to the bore. I check my fired brass for concentricity to verify the concentricity of the chamber, and after loading I re-check the loaded round for concentricity, this will tell you if you have a concentric chamber and a good/or bad loading Procedure.

If you don't turn the necks to a uniform thickness, at best you will be off by the difference in thickness and your chasing your tail.

Hope this helps

J E CUSTOM

 

[bigedp51]

When a case is fired that is thinner on one side the thin side of the case expands more and the case warps and become banana shaped. This causes the base of the case to tip and no longer be 90 degrees to the axis of the bore.

Full length resizing reduces the case body diameter and the egg shaped case body will have little to no guiding effect on the bullet. And bumping the case shoulder will allow the ejector to push the case forward. And this prevents the warped base of the case from tipping the case in the chamber.

NOTE, at the Whidden custom die website they tell you they get the most concentric cases using non-bushing full length dies. Bushing dies if the neck diameter is reduced .004 or more will induce neck runout. And at the Redding website they recommend reducing the neck diameter in two steps when reducing the neck diameter .004 or more. The bushing "floats" in the die and can move from side to side and even tilt when reducing neck diameter. Also Redding recommends to use the expander if you do not turn the case necks and use a bushing .002 smaller than expander diameter.

NECO case gauge checks the following.
http://www.neconos.com/details.htm
1) The curved "banana" shape of the cartridge case;
2) The relative wall thickness variation of a cartridge case;
3) The cartridge case head out-of-squareness;
4) Individual Bullets - out-of-round "egg shape" and/or
curved "banana" shape (excepting very small bullets);
5) The seated bullet and cartridge runout of loaded rounds. The accuracy of any firearm is determined -- and limited -- by the quality of the ammunition shot in it. The effect of imperfections in ammunition is cumulative; each flaw adds to the influence of all others.

 

[brentc]

I personally don't check for runout. I rely on quality equipment and sound reloading practices to produce consistent ammunition. IMO a lot of precision error in regards to runout is shooter induced due to the mental aspect. When you think you're shooting less precise ammunition, your groups will be less precise. I've actually heard of shooters winning matches and/or setting records with their culled high runout ammunition that they mistakenly grabbed instead of their straight "match ready" loads.

In regards to German's little article, It seems to me that the spring loaded ejector applying constant pressure to one side of a chambered case would have more effect on precision than the extractor. Unless by saying extractor, he actually meant ejector.

 

[DartonJager]

I could just SCREEEEEEEEEAM, and I'm not kidding. I strive to always produce the most accurate reloads I can but it has become painfully clear to me doing so almost demands a considerable expenditure of money. It would seam my RCBS RC press needs to be replaced with a Forester COAX press, and I need at the VERY LEAST to invest in a Redding case neck gauge and a Sinclare concentricity gauge as well as Forester BR FL sizing and bullet seating dies for all of my reloading of rifles. And my ammo is only as good as the firearm I put it in and all of my rifles are stone stock factory so even if I produce ammo with >.003" run out if my rifles chambers are less than perfect they will likely negate my accuracy potential of my ammo even if near perfect.

It's times like this where ignorance could almost be looked upon as bliss.

 

[dgarrett]

Do you dry lube your necks to try and keep neck tension as close to perfect as you can??? Do you make sure you shoot your reloads in a short time frame as dissimilar metal contact from bullets sitting in a loaded case can cause stickiness and the projectile will not release as easy... When you straighten the loaded bullets are you actually changing the neck tension by pushing them over... When you barrel a round doesn't it center everything and make it pretty much concentric with your barrel if you are just kissing the lands ( No Freebore)... These are just dome things I think of and I am sure you could drive yourself crazy striving for the perfect shooting rifle and load... Dave

 

[DartonJager]

Do you dry lube your necks to try and keep neck tension as close to perfect as you can??? Do you make sure you shoot your reloads in a short time frame as dissimilar metal contact from bullets sitting in a loaded case can cause stickiness and the projectile will not release as easy... When you straighten the loaded bullets are you actually changing the neck tension by pushing them over... When you barrel a round doesn't it center everything and make it pretty much concentric with your barrel if you are just kissing the lands ( No Freebore)... These are just dome things I think of and I am sure you could drive yourself crazy striving for the perfect shooting rifle and load... Dave

Like I said ignorance can be blissful.

 

[DartonJager]

When a case is fired that is thinner on one side the thin side of the case expands more and the case warps and become banana shaped. This causes the base of the case to tip and no longer be 90 degrees to the axis of the bore.

Full length resizing reduces the case body diameter and the egg shaped case body will have little to no guiding effect on the bullet. And bumping the case shoulder will allow the ejector to push the case forward. And this prevents the warped base of the case from tipping the case in the chamber.

NOTE, at the Whidden custom die website they tell you they get the most concentric cases using non-bushing full length dies. Bushing dies if the neck diameter is reduced .004 or more will induce neck runout. And at the Redding website they recommend reducing the neck diameter in two steps when reducing the neck diameter .004 or more. The bushing "floats" in the die and can move from side to side and even tilt when reducing neck diameter. Also Redding recommends to use the expander if you do not turn the case necks and use a bushing .002 smaller than expander diameter.

NECO case gauge checks the following.
http://www.neconos.com/details.htm
1) The curved "banana" shape of the cartridge case;
2) The relative wall thickness variation of a cartridge case;
3) The cartridge case head out-of-squareness;
4) Individual Bullets - out-of-round "egg shape" and/or
curved "banana" shape (excepting very small bullets);
5) The seated bullet and cartridge runout of loaded rounds. The accuracy of any firearm is determined -- and limited -- by the quality of the ammunition shot in it. The effect of imperfections in ammunition is cumulative; each flaw adds to the influence of all others.

Bigedp51,
I would like to invest in a concentricity gauge, and have for years considered the NECO gauge as one of if not the best values out there. I would like your opinion of it as far as it performing all a reloader needs in terms of checking his brass as well as reloads for the presence or hopefully absence of run out or other issues that contribute to inaccuracy.
Thanks,
Art

 

[bigedp51]

Bigedp51,
I would like to invest in a concentricity gauge, and have for years considered the NECO gauge as one of if not the best values out there. I would like your opinion of it as far as it performing all a reloader needs in terms of checking his brass as well as reloads for the presence or hopefully absence of run out or other issues that contribute to inaccuracy.
Thanks,
Art

I do not have the NECO gauge, I posted the NECO information so the readers would know you can have a warped banana shaped case.

If you use Forster full length benchrest dies and benchrest seating dies the average reloader would not need a runout gauge. The biggest cause of neck runout is if the expander is locked down off center.

You can buy a expander die and use your existing full length dies or just buy the Forster die with its high mounted floating expander.

The RCBS case mastering concentricity gauge is the swiss army knife of gauges. I also use it to check for case stretching and thinning and other case and neck measurements.

For price and accuracy I would recommend the Sinclair concentricity gauge. Along with the Redding case neck thickness gauge.