? on removing expander ball

[woodmann]

I've been reading as much as I can about runout and a large consensus of members seem to point to withdrawing the expander ball as at least a portion of the problem. I was wondering if removing the expander ball from the die would help to solve the problem.

Why not allow the bullet to expand the neck as it's seated. My thought is that if the case is sized then forced back open by the bullet, neck tension would be as consistent as a case that had been expanded by an expander ball. I realize that necks that had been turned would theoretically expand more uniformally, but in my mind this should at least help turned or unturned necks.

What am I overlooking?

I know this would only work with boattail bullets.

 

[jmorris]

Re: ? on removing expander ball

If the rim is dented the expander fixes it. If you remove it, it can't.

 

[TresMon]

Re: ? on removing expander ball

Umm no this is irrelavent as to whether flat base bullet or BT.

The thing to do is
1. pull the expander ball out of the die.
2. resize several/many fired cases.
3. mic the inside dia. of the case mouth.
4. do the math and see how much smaller the resized case mouth is than the bullet. This difference is called "neck tension" in the hand loaders world.

I.e. if the case mouth is .004" smaller than bullet dia it's referred to as .004 neck tension.

For a bolt gun you want .003" neck tension for a hard use, detachable box mag fed bolt gun.
.002"ish for ultimate accuracy generally

More for a round slamming auto loader.

So let's say after you pulled the ball out of the die and sized the case you'd be getting .006" neck tension.

Chuck the expander stem, with the ball on it in a drill. Turn it with the drill and polish the ball down a thousandths-inch at a time or two and go run the ball into the case mouth.

Measure the case mouth.

Keep polishing the ball down (with FINE [600 grit or finer] sand paper) until you get the correct neck tension.

Go easy on the polishing. If you make the ball too small there is no going back, Time to order a new ball. Cheap enough but a pain in the neck.

addendum: this is assuming you have conventional dies. The best fix is to use "neck bushing" dies. The individual bushing that resize just the necks can be changed so your getting the exact neck tension you need and an expander is not used.

 

[Graham]

Re: ? on removing expander ball

There's nothing wrong with removing the expander ball. But if you are running a gas gun you will need some way to round out the case necks.

Without an expander in place there is no way to true the inside diameter of the neck. So, if the neck walls of the brass are inconsistent the inside of the neck will not be round - the thick spots will be pushed to the inside by the sizer die. Therefore you are not elinimating runout, you are only reducing measured runout. Big difference.

 

[Greg Langelius *]

Re: ? on removing expander ball

I've tried that and other techiques as well, and checked their effectiveness in blind tests. For me, the accuracy differences wer not glaringly signficant, and I suspect this might have been because all my rifles have chambers that conform to SAAMI specifications.

It just doesn't seem as if concentricity makes much difference until it reaches the point where it's visible to the naked eye (rolling the cartridges on a smooth surface) where SAAMI chambers are concerned.

I would suspect this becomes more critical when tighter necked chambers are involved.

I also found that as neck tension went up, accuracy decreased.

Greg

 

[9H_Cracka]

Re: ? on removing expander ball

What you are overlooking is the fact that the last thing that touches the neck is what determines its dimension.

A conventional die is set up to have the expander be the last thing that touches the neck, after the die has tightened the neck smaller than the dimension the expander will take it to after passing through.

By removing the expander in a non-bushing die, you are left with neck tension that is most likely tighter than what you want.

Your assumption that doing this would create more uniform neck tension is flawed, in that on unturned necks, sizing off the ID produces more consistent neck tension than sizing off the OD, as sizing off the ID is only affected by the springback differences between neck wall thickness, whereas sizing off the OD is affected by both neck wall thickness AND springback differences.

This is why ID mandrels are in the Sinclair catalog.

 

[turbo54]

Re: ? on removing expander ball

My opinion is that .002" neck tension (annealed brass - more on that later) is sufficient for bolt guns and autoloaders.

For some reason (and it defies my engineering sense), final sizing the neck ID with the expander ball (in tension) produces more runout than doing it in compression with the sinclair tool. Why is the sky blue? How's a rainbow made? Hows the posi-trac in a Plymouth work? It just does.

The "ultimate" as far as I'm concerned (and I don't do the neck turning thing - that sucks), is using a bushing to size neck OD such that your ID is left .003-.004 UNDER bullet diameter, then use a sinclair expander die with a "neck turning mandrel" to final size your ID .002" under bullet diameter, leaving you with .002" neck tension.

On neck tension: There is a limit to how much you can truly have. Imagine a caseneck with an ID of .200". Then you seat a .308" bullet into it. Now pull that bullet back out and remeasure the caseneck ID. Think it's still .200"???

It's not. Why? Because the brass yielded and stretched.

In my opinion, annealed brass (such as out of the box Lapua), is capable of NO MORE than .002-.003" neck tension. I haven't performed a study to determine exactly how much this will increase as you work the brass, but it WILL go up as the brass gets worked more, becomes harder, and the yield strength increases (as all metals do).

 

[MitchAlsup]

Re: ? on removing expander ball

A bolt gun in benchrest activities can use as little as 0.000 in neck tension. the cartriges are subject to no stress between the loading station and the final firing position. The more typical benchrest or tactical practice session is served with neck tensions in the range of 0.005 to 0.001.

A bolt gun in tactical situations where the cartriges are subject to mild abuse from the loading station to the final firing position wants 0.002 in neck tension. The tactical shooter wants everything to be consistent all the time, so the neck tension of the practice rounds should be identical to the neck tension of the actual tactical round.

A semi-auto can generally get away with 0.003 in neck tension. The extra tension prevents the bullts from being slammed backwards into the case as the action cycles violently, and prevents the bullet from rushing forward as the actionlocks rapidly on the newloy chambered round.

The word-pair "neck tension" is a misnomer. Tension is defined as a force and is not measured in thousandths of an inch, but measured in Newtons. The thickness of the brass, the metalurgy of the brass, and the number of reload cycles after the last annealing cycle alter the linear measurement to the actual grip the case has on the bullet.

 

[Fuzzball]

Re: ? on removing expander ball

"I also found that as neck tension went up, accuracy decreased."

There's the answer; using a bullet as 'expander' during seating simply means you are be using the worst possibly aligned tool to do a critical job.

My experiments have shown that any neck 'tension' more than about 1 thou is meaningless for actual bullet grip. A smaller neck ID than about 1 thou simply increases seating force while the bullet stretches the neck passed it's elastic limits. (That's average, the springback does vary a tiny amount depending on how hard the brass is.)

I get the straightest possible necks and proper 'tension' (actually that's what mechinests call an interferrence fit) with Lee's Collet Neck sizer. Add a body die if I want to do a "FL" size job. I usually buy a used sizer (cheep) and bore the neck slightly oversize to make my own 'body' dies.

 

[Tripwire]

Re: ? on removing expander ball

If you are a full length non-bushing-die resizer like me, then the answer to drastically reducing runout caused by the expander is to simply buy a second FL sizer die. I use Redding FL dies, and in one sizer die the expander stem is removed permanently. This die sizes the case with a .001" bump of the shoulder on annealed brass.

The second die has the expander stem installed but adjusted down far enough that it would be impossible to push a case all the way in. This expander stem has the Redding carbide floating expander ball installed on it. To use you simply push the already FL sized case's neck UP over the expander ball in a second step.

This action of pushing the neck up over the expander, instead of pulling it down over the expander, has all but eliminated runout for me with FL sizing, when used in conjunction with a comp seater.

 

[Graham]

Re: ? on removing expander ball

A sizing ball is better, but it can grab regardless of whether it is pushed in or pulled out of a case neck. Centering the expander in the die helps, too, which is why lower in the die is usually worse.

Expander harm is proportional to the amount of sizing done by the ball. That's why thicker case walls cause more problems - because the case neck is first sized on the outside, then on the inside, and thicker walls increase the total reduction...another reason why harder brass makes controlling this problem all that much harder.

 

[woodmann]

Re: ? on removing expander ball

Wow, Thanks for all the insightful replies. I hadn't considered the dented neck being a problem. I was thinking of trying this in a bolt gun, but it is still a good thought.

It seems that a few of you understood what I was asking and a bigger majority may not have. With that in mind I'd welcome any followup from anyone.

I'm not looking for <span style="font-weight: bold">more</span> consistency in neck tension by removing the expander ball. I was thinking that by sizing the case and not pulling it back over the ball (I use RCBS dies at this time=knurled expander ball which feels about as smooth as wiping with a pine cone) that the chance of maintaining the truest shoulder and neck could be improved.

I was thinking that pushing a factory polished boattail bullet into an admittedly undersized neck would be a smoother and less destructive (to the case) operation that dragging a knurled expander back up through the neck unsupported. (I still don't think that I could get a flat based bullet started into a neck that is probably eight-ten thousandths (a guess) undersized without damaging the neck or shoulder.)

Maybe Greg L. told me all that I need to know in that he has tried it and failed to notice an appreciable difference in accuracy with a SAAMI chamber, which is what I am shooting.

Many have commented that over 2 or 3 thousandths of "neck tension" causes you a decrease in accuracy. This may be enough to make it a non-starter right there in that whatever theoretical advantage is gained in my premise, is lost due to increase in "neck tension."

Hopefully this will bring clarity to my original post and possibly spark futher insight/debate.

Thanks for looking.

 

[Graham]

Re: ? on removing expander ball

The bullet is not a sizing tool. If you want to do that, get a mandrel.

 

[Clark]

Re: ? on removing expander ball

I have the Sinclair concentricity gauge, and there was a Chinese fortune cookie fortune that came in the box that said, "You will probably find that the expander ball is the problem."

That may be valuable advice, but is an over simplification. The problem is factory rifle SAAMI chambers with over sized inside diameter necks and off the shelf full length sizer dies with tiny inside diameter necks. Between the two of them, the case neck gets way bigger than it needs to be, and then way smaller than it needs to be, then the expander ball makes it closer to what it needs to be, but pulls it .004" crooked if done in the sizing step. The same expander ball does far less damage if used in a separate step of pushing in, but I have seen few jacketed bullets that could not push their own way in.

I hand load 26 different bottle neck rifle cartridges and own a lot of different kinds dies. But when I get a new cartridge I do not buy a lot of dies for it. I have now narrowed it down. I now just get a Forster full length sizer die and pay Forster to hone out the neck to .002" smaller than my finished ammo. I can hone my own, but they do a great job and don't charge much. I also get a Lee Collet neck die and, in the lathe, polish the collet, collar, and mandrel/ decapping pin. Polishing does not make any more concentric ammo, just a smoother feel pulling on the press handle.

The other thing I do is buy custom chamber reamers with no turn necks. That means the chamber neck is just big enough to fit ammo with necks that have not been turned down. I only bother with this for small game cartridges. Big game is fewer shots and bigger targets.

.223 is SAAMI registered at 55 kpsi, but if I shoot a piece of brass at 66 kpsi for 15 times without annealing and without trimming, and it is still very concentric, then I got my money's worth out of it.

Benchrest guys with 6mmPPC typically have even less neck expansion in the rifle and less constriction in the die, than I do. So my system is half way between expander ball crooked necks and benchrest fussing over .0002" on turning necks.