Run-out help needed

[Mikecr]

idefendem, RUNOUT and perceived CONCENTRICITY are two different things.
And the Hornady neck bender is not a valid solution for either.

I don't understand all the implications that fireforming would create runout.
Fireforming is the ONLY way to straighten cases, and it works very well.
Take a new case, measure it's runout off necks. Now load it, fire it, remeasure -runout reduced.
FL size it, remeasure -runout returns.
Repeat this cycle -runout grows.

Now you can index/mark the case to see a bow develops in this, and yes it follows thickness variance.
This is why neck bending is in no way a solution. It doesn't straighten a case that will be rechambered.

Solution:
#1 Cull by thickness variance
#2 Size minimally
#3 Determine & manage additions to loaded runout

 

[Bart B]

Take a new case, measure it's runout off necks. Now load it, fire it, remeasure -runout reduced.
FL size it, remeasure -runout returns. Repeat this cycle -runout grows.

Now you can index/mark the case to see a bow develops in this, and yes it follows thickness variance. This is why neck bending is in no way a solution. It doesn't straighten a case that will be rechambered.

Not so in my experience and that of others.

I measure bullet best relative to the middle of the case shoulder and 1/10th inch back from the bullet tip with the case pressure ring resting at its back end. That's how the round fits the chamber. Multiple full length sizings with a die whose neck diameter is 2/1000ths smaller than loaded neck diameter on a given case did not change the runout numbers on a 47-shot test with the same case full length sized every time. A friend put 57 shots from a single .308 Win. case so sized into 1/3" at 100 yards in his test with his rifle in a machine rest.

Neck bending's always got me better accuracy with military M118 and M852 match as well as commercial match ammo. They've typically got 8 to 14 mils TIR for military and 3 to 8 TIR for commercial, half that for standard runout. Bent hundreds of 'em as they're held in a .338 caliber bullet puller on the case neck, then pushed the case head away from the runout high point. Got 'em back to no more than 6 thousandths TIR. Improves accuracy at 600 yards by 1/2 to 3/4 MOA. Been there, done that; know very well how much it helps.

 

[Mike027]

I just resized a few more cases of brass that have been fired 6 times.

I use rcbs case lube. I dont use a lot. I dont put any on the necks and I run a brush with a touch of oil into the neck. If I dab the case mouth into the lube pad and then resize the die there is an awful screeching noise on the downstroke. It always make that noise if there is too much lube and it doesnt take much. Im not sure if this is normal. ????

There was less than .002 on the fired cases and not much of a difference after resizing.

I checked the width of the case necks with a digital caliper before resizing and they measured about .340 and after resizing they measured about .330

Does this sound about right? Mike

 

[ajhardle]

Careful putting case lube in the mouth, some say a gob of it would affect burn rate. I never felt a need to do it, but you should use a dry lube.
I am surprised to here that your seeing that much run out on an unsized case, considering it should match the chamber pretty closely.
You're sizing the case neck diameter .010, according to your measurements, which is normal for a factory chamber, but the important measurement is constriction. Tell me how much that neck diameter grows when you insert a bullet. Most of my concentricity problems were from to much tension when forcing a bullet in there.
I like to see no more than .002" constriction. For example after a sized case measures .330, it should measure .032 with a bullet in there.

 

[Bart B]

Lots of folks lube their case mouths before resizing the case with an expander ball on the decapping stem. As most dry lube's an abrasive (graphite?), I cringe at the though of blowing that stuff down the barrel. And what a liquid lube turns into from all the heat of powder burning may not be good for the bore. I admit some ignorance in such issues, so I choose to do things on the side of safety and bore preservation.

Before I started using gelded dies (those without balls of any kind) with neck diameters 1 or 2 thousandths smaller than a loaded round's neck diameter, I cleaned out the powder fouling inside case necks with a bore brush before tumbling or vibrating them to clean their outsides off. A bore brush size that's a tight fit in a fired case mouth does wonders getting rid of that hard powder residue that ain't slippery enough for an expander ball to come up through the tight case neck without screaching bad noises into our ears. After bore brushing case mouths and cleaning them, when lubed correctly they ended up with straighter necks on the case. Once the lube's cleaned off, then primed and charged with powder, seated bullets had less average runout than fired case with no case mouth cleaning/brushing.

 

[Mike027]

The cases measure .334 after the bullet is seated. I thought that seemed a bit odd. I read on another forum that the Deep Curls are a larger diameter than comparable bullets. I'm considering purchasing a Forster sizing die and their bench rest seater to see if it helps. Is there a particular brand of dry lube I should purchase? Mike

 

[Bart B]

Mike, I don't think any seating die will make up for crooked case necks. And the smaller a case mouth is relative to bullet diameter, they harder it will be to seat bullets straight. Redding's web site has an interesting read about this:

Neck Runout With Bottleneck Cases

The concentricity, or neck runout, of loaded cartridges is an important consideration for reloaders and especially the varmint or target shooter. There are many factors that can cause or contribute to neck runout during the reloading process and many reloaders who have not dealt with the problem before quickly blame the sizing or seating die.

While the dies may be at fault or have a contributing defect, modern CNC machinery and reamers that cut the body, shoulder, and neck simultaneously make such occurrences rare. Most problems are related to the brass itself and its uniformity both in terms of hardness and thickness and how much it is being stressed in the reloading process.

An entire book can be devoted to this subject, but the amount of stress the brass is subjected to can be your key to finding a problem. If you "feel" any difficulty and /or heavy resistance when resizing your cases this can be a telltale clue.

Excessive difficulty while resizing can indicate any of the following: Poor choice of case lube, failing to clean the die and/or brass, faulty polish inside die, chamber large or at maximum S.A.A.M.I. spec resulting in excessive brass resizing. A large neck diameter in the chamber combined with brass that is thin or excessively turned can cause crooked necks in a hurry. The more brass has to be moved the more its residual memory takes over.

Resistance to pulling your cases over the size button can indicate problems. A "squawk" says "shame on you", you forgot to brush the residue out of the necks. A hard drag can indicate that the top of the size button is not smooth. Don't be afraid to polish the top radius with #600 wet paper, but don't reduce the outside diameter or you can create an excessive bullet fit. Carbide size buttons are now an option also; they have a lower coeffecient of friction.

We have conducted many tests over the years on the various factors contributing to concentricity problems with bottleneck cases. We have repeatedly found a definite correlation between the uniformity of the brass (or lack of it) and the resulting concentricity of the neck to the body of the case.

An interesting experiment also revealed that neck turning of brass that was intentionally sorted as non-uniform, showed little or no concentricity improvement when used in standard S.A.A.M.I. spec chambers. Conversely brass that was sorted and selected for uniformity remained uniform and concentric with or without a neck turning operation.

Another interesting observation can be found in the examination of fired cases that have crooked necks "as fired" right out of the chamber. Usually the chamber is being blamed for the problem.

Looking at the primers under magnification you can usually find a telltale machining mark or other blemish that was imprinted from the bolt face. This will give you an index mark with reference to the chamber. Mark this index mark on the cases with a felt tip marker and go about checking the concentricity. If the runout is random to your index marks the problem is not the chamber. Further examination will show the same correlation with the good and bad brass.

Note that to this point we have not talked about seating dies. That is because 98% of all concentricity problems exist in the brass prior to bullet seating.

Keep in mind that no seating die ever made will correct problems. The best you can do is to obtain a quality seating die that does not add any.

It's been my experience that full length sizing dies with necks sized about 1 to 2 thousandths smaller than a loaded round's neck diameter ends up making the straightest case necks on case shoulders. Either a full length bushing die or a standard die with its neck lapped out. Here's what Redding has to say about sizing dies and case necks:

From tests we have conducted, we have learned that selecting the correct bushing is the most important factor in producing sized case necks that have good concentricity with the case body. Our tests showed that case neck concentricity is directly proportional to bushing size. In other words, as you size case necks with progressively smaller bushings, the concentricity gets progressively worse.

Our current recommendation, is to select a bushing that is .001 to .002" smaller than the loaded cartridge neck diameter. For example, if the neck diameter of your loaded cartridges is .248", start with a .247 or .246" bushing. We've had to change our initial recommendation, because some of cartridge cases manufactured today have neck walls near the minimum SAAMI thickness. When using brass which is at the thinner end of the SAAMI spec. we have found the bushing which is .001" smaller will provide the best result.

To create precision reloads, you must start with cases of good quality. They should all be from the same manufacturer and lot number. A good measure of case quality is how uniform the neck wall thickness is. Cases with uniform neck wall thickness, will be of uniform thickness all the way to the base. This is important for accuracy, as the cases will expand uniformly upon firing, and contract uniformly when sized. Neck turning helps, but it's only a partial cure, as you can't turn the case wall all the way to the base. The Redding Case Neck Gauge is the preferred instrument for checking neck wall thickness and uniformity. Also note that the concentricity of a fired case only indicates how concentric your firearm's chamber is. It provides you with little or no information on the quality of the cases you're using.

I have no idea what a good dry lube brand might work.

 

[Mikecr]

If you run across a chamber that produces crooked cases, you might as well spin off the barrel & pitch it in a nearest dumpster. I've had some pretty bad factory barrels, but have yet to see a crooked chamber. I don't even know how that could happen.

And if you're relying on dies to straighten crooked cases, your chasing your tail. Dies don't do this.
The best you achieve here with ANY die sizing, is least added runout.

 

[CogburnR]

If you are getting a squawk when pulling the case out of the die you have lube problems.

The neck should be cleaned and lubed on the inside.I'd go get some Imperial sizing wax or similar and try it.

The squawk is from the expander button opening the dry case neck back up after the neck was sized down by the die. This is also when the necks are bent.

 

[Mike027]

I don't get any Squawk if I use a very small amount of lube on the case brush. On a reloading video I had seen someone dab the case mouth into the lube pad. I tried it and I get the squawk each and every time. It never happens when I use the case brush. Maybe it's because the brush adds the cleaning component.

I can see that during the seating process many of my rounds end up having a fair amount of added runout compared to the resized cases. Maybe I shold just try a different seater in addition to the brass prep.

This may soud silly but does anyone know PGA video link that clearly shows what happens during the resizing step? I'm a little confused on what actually occurs inside the die. Mike

 

[ajhardle]

I would think your run out problem it's from to much neck tension. You said it measures .004 larger with a bullet seated.

I just finished two batches, and the first using a lee collet neck die, showing about .001 neck tension, and the most run out was almost .003. Average was less than .002. This brass was not neck turned.

The second batch was sized with a lee full length die, with twice as much neck tension, but still less than .002. I measured neck concentricity that was double the previous batch's numbers, and bullet run out was also doubled.

But to be fair one batch was Hornady brass loaded in a single shot savage, and the other Lake City for an AR15.

Another benefit of the lee collet die is less working of the brass. Not having to trim brass means fewer steps in my reloading. I just wipe the brass off with a cloth. No tumbling, no messy lubes. And that makes me happy.

 

[Mike027]

I think I will go ahead and order the Lee collet die and give it a try and see what kind of results I get. Everything that I have read about them is positive. Thanks. Mike

 

[Bart B]

The Lee collet neck sizing die, like all other neck only sizing dies that don't hold the case shoulder and front part of the case body well aligned with the case neck, don't do as good of a job of keeping the case neck well centered on the case shoulder. Which is why this die is not popular (and rarely, if ever, used by folks shooting the best scores and smallest groups in competition. If one' not able to measure the runtout of the case neck relative to the shoulder on a sized case, they'll typically not be able to see this issue. Case necks need to be well centered on all bottleneck cases that headspace on their shoulders. It's the case shoulder that centers the front of the case and therefore the neck and the bullet it holds in the chamber when the round fires; if the case neck ain't centered on the shoulder, there's no way it'll be centered in the chamber neck.

Virtuall all the benchresters gave up on neck only sizing years ago and have switched over to the full length sizing dies with bushings of the correct diameter for their case necks. Such dies keep the case neck well centered on the case shoulder but size the case body and neck down very little and set the fired case sholder back a thousandth or so. Sierra Bullets was probably the first place where enough proper tests were made with various sizing dies and techniques back in the 1950's. They've been using full length sizing dies ever since; nothing else sized cases good enough dimension wise to shoot their bullets into the smallest test groups. Nowadays, they use Redding full length bushing dies or standard full length sizing dies on their fired cases to resize them. Those dies work the same way and use the same bushings as the ones made by RCBS.

So, Mike027, if you've read this, you have read something about collet neck sizing dies that's not positive. And I think ajhardle's comment on your sized case necks being too small is a good think to consider. There's probably enough force on the case neck from the bullet needing so much force to seat it that the case neck's pressing down hard enough on the case shoulder to bend it. This can be seen if you can measure neck runout on a sized case. But you'll have to have the front rest on the case at mid point on the shoulder, not on the bullet, case body or case neck to see it.

All the above aside, if one does not use a good quality full length sizing die and/or set it up and use it correctly, they may well get better results by some neck only sizing method.

 

[Mike027]

Oh snap I already ordered the Lee Collet Die from Cabelas just before midnight. I won't be out a lot of money if it doesn't work. In a couple of weeks I should be able to load some up and give them a try. Mike