Concentricity

[ElJay]

I need some help understanding the issues regarding concentricity. I am presently shooting and reloading 223 Rem. The cases are from LC XM 193 5.56. I am resizing with either a FL full RCBS re-size die or a Redding neck die. After decapping, I clean with walnut shells in a vibrator, then trim to length, chamfer, anneal and then ultrasonic clean. I seat with a Wilson seating die.
Out of 100 cartridges, using a Hornady concentricity gage, on average, I get 35 with less than .001 runout, 55 between .001 and .002 and the remainder are have runouts greater than .002. These measurements are taken at or near the ogive. If I now run the indicator farther down the case I get corresponding runouts. Generally, the high spots line up down the length of the cartridge- but not always. I have had cases where the ogive ran out .003 and the head of the case was dead (0 runout). On the other hand, the ogive could run dead and the rest of the case looked like the Pillsbury Doughboy.
I have also run some tests where I measured the neck thickness before seating the bullet. Concentricity readings in no way correlated with the neck thickness values. Generally the wall thickness was in the order .012' plus or minus .0005"
I have several questions:
1. Are these results a product of the brass or the dies?
2. What is supposed to be concentric to what?
3. What else am I missing.
By the way, except for the cartridges where the bullet runs out greater than .002, they shoot in the area of .6 moa at 135 yards.

 

[SS427]

You are getting 90 out of 100 cases with .002 or less runout; I would say you are doing really well. I can't say I do any better with Lapua brass.

I would say what little problem you have is your brass. 35% at .001 or less tells me the dies are fine.

 

[amlevin]

I'd concur. Even switching to "Competiton" or Inline dies may not improve on that.

In a perfect world everything would be concentric to the axis of the bore from muzzle to firing pin. All bullets would enter the bore perfectly centered. Case would position it in such a manner that would make this possible. Now enter the bolt. Does it hold the sized case perfectly centered? When the cartridge is fired does the case head meet, and get "formed" against a bolt face that's at a perfect right angle to the axis? If not, then the next time you load that case it will be "bent" in a different direction unless you indexed the case when you extracted it and then made sure you chambered it exactly the same.

So many variables. I certainly wouldn't worry too much about +/- .002" runout. Doesn't sound like you have a match chamber (thus the pillsbury dough boy) nor are you using any special dies. This sounds great for what you have.

 

[MrMajestic]

Generally the wall thickness was in the order .012' plus or minus .0005"

??? .012 ft. = .144"
They should be able to handle some serious amounts of pressure!
Probably hard to resize. ;D

 

[Leaddog]

Decap, clean, anneal, FL resize, trim and chamfer, in that order.

 

[Shynloco]

IMHO, considering you are NOT using Lapua brass, you are getting outstanding results in terms of concentricity with that LC brass. Like others have said, your dies are fine. But a question I have, is are you reloading for competition and are you shooting a Match Grade barrel? If not, then even if you come up with 100% of concentricity at or below .001 won't get you the same results in grouping or scoring as a rifle built for competition would. In short, concentricity is but one factor in the quest for that repeatable perfect score and there are several other "VARIABLES" that matter. Lake City ammo and casings are very good, but wouldn't be my choice if I were loading for competition purposes. On the flip side, I'd recommend you use the casings with the .001 - .002 concentricity casings for score and the others for foulers. And having been down the road with several caliber casings even when its Lapua brass, you simply will get some pieces of brass that don't have good enough necks when manufactured and you cannot correct their deficiency. Hope that helps some.

BTW, as to your question on what should be concentric to what, the idea is consistently center the bullet to the center of the bore so that the bullet enters the bore when fired exactly centered each and every time. A bullet even slightly off center or canted will create that infamous flier or expanded grouping.

 

[fdshuster]

ELJay: What you are seeing is variances in the brass. Some brass is close to perfect when it's drawn and others not so perfect.

I can take any brass, even the superior Lapua, using neck bushing dies and a Wilson chamber seating die (with an arbor press), and even some of that brass will have loaded round runouts of as much as .003".

With Lapua it will only be a very few, but with other brands like Winchester, Lake City, Remington, etc. it will usually be more than a very few.

If it were a problem with the dies or your loading practices it would stand to reason that all the rounds would have large runouts.

I mark the rounds with more than what I consider to be acceptable R/O, and use those rounds for fouling shots, basic scope sight-in & informal, not match, shooting. Surprisingly I've gotten some excellent 5 shot groups at 100 yds. with ammo that has as much as .005" of R/O.

A few cases will straighten out after 2 or 3 firings, but others will never straighten.

 

[mikecr]

Forget concentricity.
The best we can do is make STRAIGHT ammo that's headspaced correctly, as straight is also concentric(not the other way around).
If you're measuring anything off the ogives with a Hornady concentricity gage, you have some pretty high runout. That runout would show on a V-block type of gauge(Like Sinclair).

It should be very rare that any FL sizing is needed for a 223(for a bolt gun). And with this, it would be very rare that any trimming or annealing would be needed. FL sizing increases runout with each cycle.
Also, it's hard to believe your unturned necks are all under 1thou of thickness variance. I've yet to see this(consistently) in lots of Win, Norma, or Lapua. How are you measuring this?

If I were you, i'd partial NS with a bushing 3thou under loaded neck diameter, and use a Sinclair expander mandrel with each neck(not the die's).
Forever stop FL sizing and annealing, but use a Redding body die to set headspacing when needed.
Get rid of the Hornady gauge, and pick up a NECO or Sinclair.