Concentricity, how I fixed mine

1. How much oblique force is needed to bend the neck of cylinder with .012 - .015 walls of brass.

2. What is causing this oblique force? in my dies the seating stem contacts the bullet at some point on the ogive and contacts it equally on all sides. There is only downward force. The case necks are chamfered to guide the bullet in without the brass scarring the bullet and even on flat base bullets there is a slight radius

3. What would cause the bullet to not follow the path of least resistance and follow the interior walls into the neck ?
 
1. Are you sure that's what you see? Check for runout at different points along the neck to see if you don't just have lopsided expansion over the bullet.

2. The same thing that pushes radially outward from the case axis to expand a neck on the inside from as-resized to bullet diameter during straight seating. It's the wedge principle.

3. Of course it follows the path of least resistance, but resistance to entry into the neck isn't the only resistance in the overall seating mechanism. If the mouth of a seating stem of the type that commonly puts a ring mark on a bullet starts biting into the ogive before it fully straightens, it can resist further straightening. That can be more resistance than the lopsided expansion of the neck requires to overcome.

Incidentally, in dies that would seat bullets slightly cocked, I noticed coated bullets tended to seat a little straighter, and I suspect lubrication at the contact point with the seating stem opening was responsible. I think this may also explain why tests Dr. Ken Oehler did at 1000 yards with moly-coated vs. uncoated bullets, resulted in a very slightly higher ballistic coefficient (slightly shorter TOF) for the coated ones. A lower level of initial yaw due to being seated straighter could account for that. But I am speculating as I recall the test (in an issue of Precision Shooting) result was on the raged edge of statistical significance.
 
I wish that site included the original post dates so you could see which article is older.

Part of the attraction of the Wilson dies is the compactness of the little arbor presses. They make for a nice range loading kit.
 
I am not saying that the Wilsons are bad dies by any means. I have a arbor press and 3 of the Wilson seaters myself. But a Wilson will not straighten a neck that is not concentric going into it. If the necks are not concentric going into the seating operation the ammo will not be concentric coming out of whatever die you are using.

It's all about the case prep, I can seat using the Wilson dies or with the Frankford Armory Universal and get concentric ammo. That bullets bearing surface will follow the neck walls regardless
 
I don't think concentricity matter's much to the hunter. Actually I'm pretty sure of it. Been handloading well over 50 yrs, am a hunter and have never worried about it. Most modern rifles I can get shooting well under an inch and that works fine for a hunting rifle. I even have several rifle's that go down around 1/2", how much is required for a hunting rifle? Of course if your a rifle competitor where .002" might make the difference between 1st and 2nd, then I might get it. I don't measure distance off the lands either, simply make sure I'm not touching, in fact even doing that might be over kill for a hunting rifle. Guarantee no factory will lay claim to ammo @ x # inchs off the lands of every rifle and yet there are reports of great shooting factory ammo.
 
Depends on what you are hunting and at what range.

For larger game, most likely it rarely matters unless you are taking very long (400+ yard) shots.
Not all that common for most hunters, and unless you are SURE of accuracy it can easily move out of reasonable fair chase and sport.

For Varmint hunters 'minute of varmint' is a lot smaller
and they are often rather skittish.
I get invited by farmers to "clean out hose damn groundhogs." Usually after spring planting and they notice the damage that has been done at the edge of a field.

Shots over 400+ yards are not uncommon.
The critters will dive to burrow at the sight of a person at 300 yards, and some even further if they have been hunted over repeatedly.

So I steal all the BR techniques I can, right down to using Stolle Panda actions (right bolt, left port, no ejector), no mag cuts, Jewell BR triggers (less than 2 ounces), synthetic stock, and shooting rests. BR grade barrels (usually cut rifling), attention to runout, concentricity, etc.
The actions are not for weight, but for precision and the ability to reliably change barrels (and calibers) in the field.
It is not a quick process to acquire target critters.
Search with 10 x 40 Pentax field glasses.
Pinpoint with a 60x82 Kowa scope.
The scope on the rifle is a Leupold with a power doubler (Premier Reticles when they still did that work) so it goes up to 40x.

I spent many hours shooting (pretty much wore out a few barrels in .22-250AI and 6mm REM AI)) checking for any movement in point of impact over scope power and range (200 yards to 600 yards).

When sited in at 200 yards there is no detectable movement in group center.
Set up, start finding critters.
Usually one shot after about 30 to 45 minutes.

Good thing they are dumb enough to come back up after 35 to 55 minutes.
It makes for a nice relaxing day.
And farmers watching though the spotting scope and yelling "You got em. You got em" after each shot.
Most prefer my one shot, one critter.
 
hounddawg said:
But a Wilson will not straighten a neck that is not concentric going into it.
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Yep! That's what the article I linked to confirmed. But if you have prepped cases with a uniform chamfer to center the bullet base and the seating stem catches the right part of it nose, it should go in pretty straight.


Don Fischer said:
I don't think concentricity matter's much to the hunter.
Click to expand...

A simple test is, for the kind of hunting you do, does commercial ammo work well enough? You'd have to measure your box to be sure, but I don't recall any commercial hunting ammo I've had being any more concentric than military ball ammo I've measured.
 
it's that .2 to .3 of the bearing surface being squeezed by the neck walls that determines how the bullet sits, if that cylinder is parallel to the case body, the bullet has no choice except to be parallel also. Of course the neck walls must be uniform thickness also.

A buddy of mine at the club never competes, he likes beanfield deer hunting and makes a couple of trips each year out west to slaughter P Dogs. He would be hard to beat if he did compete, I saw him nail a half dozen clay pigeons in a row sitting on the 800 yard berm one afternoon. His rifles are all customs put together by long range smiths
 
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Start with a heavy duty chamfer on the inside of the neck, whenever possible use boat tail bullets and seat them with an in-line seater. I use Redding and Wilson, I don't turn necks unless it's a wildcat with a tight neck. Mark the cases that show excessive run-out and if they continue to on a second loading throw them in the trash.
There are cases that regardless of turning the neck, primer pocket squaring, flash hole drilling and chamfering, annealing necks, squaring the base or repeating magical incantantions over them will throw shots out of the group, don't loose sleep over them.
 
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hounddawg said:
I wonder if problem cases are caused by either a bent rim or possibly uneven neck brass thickness ???
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Both neck and shoulder wall thickness uniformity is needed to minimize neck axis runout. Especially when the expander ball enlarges neck diameters. I doubt bent rims matter because they don't touch the die.

This was proved in the 1950's and best quality sizing dies didn't use expander balls because their neck diameter was a couple thousandths less than the loaded round neck diameter.
 
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you are probably right about the rims Bart.

One thing I need to start remembering to do is to deburr the necks before sizing, thinking maybe a uneven burr on the mouth could get pushed to the inside. I think maybe it could get pushed back out by the mandrel maybe.....hmmm something to ponder while I mow my yard
 
Uneven case body wall thickness causes what Merrill Martin used to call a "banana-shaped" cased, and he had some experimental evidence to suggest they should be culled. I've also run into cases that had surprisingly uneven wall thickness just forward of the web. I didn't document its effect but I can't imagine it would help, so I culled them, too.
 
Nice looking tool Roper, also a interesting case/neck straightener. Key is though preventing misalignment. My Hornady tool sits on the shelf except for spot checks
 
My favorite 30 caliber case neck straightener tool is a 33 caliber bullet puller. With the loaded round's neck gripped by the collet, push the case head enough to get the neck straight.

That Neco gauge's front reference touches the case where it isn't against the chamber when the primer fires. If it was on the case shoulder, it would be perfect because it's what centers the cartridge neck and bullet in the chamber when fired.
 
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Uneven case wall thickness indicator is its pressure ring. High point is where wall is thinnest

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Last box I had of Rem BR brass, primer list on box is small rifle primer 308 and look like flash hole been drilled out. What else you do to those cases?
 
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