Advanced theory on proper size of a cast bullet expander

[gloob]

Gloob's unified theory of bullet expanders - why some folks need em, and need them BIG, and why some may think a 2 mil under expander is doing something when it's not, and why some people use the Lee Universal Expander with good success. I'm hoping to get some feeback/criticism.

It is no surprise to any members active in this forum that Gloob has some strange ideas, and he has an annoying tendency to spout his own opinions as if they are fact. Well, I formulated a pretty interesting and comprehensive "treatise" on what is the perfect size for an expander, the other day. And with what I came up with, you will may need an oversize plug, and you may not. That is nothing new, you say. But maybe there's more to it. Anyhow, I came up with some of the details in response to a query/challenge I received, after I had spouted off a bit concerning my ideas on another forum. And here is my response, mildly edited:

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http://images.thehighroad.org/statusicon/post_old.gif Yesterday,
11:16 PM

#32 (http://castboolits.gunloads.com/showpost.php?p=9921022&postcount=32)




GLOOB (http://castboolits.gunloads.com/member.php?u=53020)



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Join Date: September 16, 2007

Posts: 5,675






In my estimation, which is worth
at least twice what you are paying for it, I figure a proper expander ought to
be about 1 ten thousandth of an inch smaller than the bullet at the case mouth.
And then starting about 2 tenths of an inch from where the base of the bullet
seats, it should start to taper to 3 ten thousandths of an inch smaller than the
bullet and should reach at least as deep as your bullet will seat by the time it
adds just a little flare. And the flare should be about 3 thousandths of an inch
larger than bullet diameter. And that would be the same answer, no matter what
you are shooting, although with jacketed bullets you are probably just as good
going up to a couple mils smaller. So basically, the expander should be about the
same size as the bullet.

Note that this answer does not depend
on measuring the brass, at all. That doesn't matter in my book, whatsoever. As
long as your size die gets your brass undersized, a bit. Or maybe at least
enough to see a bulge with your bullets, anyway, that is all you need to know.
These expander dimensions are what I find will work with a tight sizing die.

If your sizing die is a little loose, already, then these dimensions will be too big!
But no worry, because in this case, you do not need an expander, to begin with!

My theory is that this is due to the larger die not getting the case
small enough, and that the plug will only be cycling the "spring" of the case an
extra time, increasing the "set" that a new spring takes, weakening what was
already less than full neck tension to begin with. In this case, it appears like
you should retain more of that tension by using an undersize plug (or just a
flare die, because this case doesn't need to be expanded at all). In a tight
enough case, this plug is making a new "spring" by redefining the inelastic
boundary of the metal. And because it's pushing the brass in the opposite
direction from the sizer, it's ok to get up to full bullet diameter. The
springback is going to make the case smaller by the exact amount it needs to get
full neck tension, and no more. And any set that the new spring is going to take
is going to act only in the direction that makes the neck tension tighter. So
it's kinda like either you need an expander at all, in which case these
dimensions will work. Or you don't need an expander, at all, in which case this
will probably hurt neck tension. But I contend that in no case do you benefit
from an expander that is 2 mils smaller than the bullet over the one or the
other: a flare-only die or this monster oversize expander. A two mil under expander
is either acting as a perfectly good flare-only die or an inadequate expander.

If you wanted to make the perfect mouth flare die for a caliber, which will never
reduce neck tension, and which will at least make a small improvement on a grossly
tight case then 2 mils under is, indeed, the ticket and there is a technically sound
reason that this size is the default. It's because most of the time (for the average die)
it is only flaring the mouth, anyway, and it needs to be 2 mils under to not ever interfere
with neck tension. But if your sizing die is tight, you will do worlds better by using an
expander the same size as the bullet. So if you need to make the jump up, you ought to
make it all the way. There's no point in getting somewhere between the two. If your die is
tight, a -1 or -2 mil expander won't give you any more neck tension than a -0 expander, but it
will have a much greater ability to swage bullets.


http://images.thehighroad.org/smilies/evil.gifhttp://images.thehighroad.org/smilies/cool.gifhttp://images.thehighroad.org/smilies/evil.gif

Footnote: you WILL
notice that the bullets are easier to seat, but if you compare the neck tension
of the bullet by whatever method you use to test that, I predict you will find
the neck tension is essentially unaltered. Again, provided that your size die is
tight enough to begin with. In fact, using a full bullet diameter expander with a
tight size die will give more neck tension than ammo made with a "good" sizer
that doesn't require more than a -2 mil expander.

[runfiverun]

your ideas on neck tension are spot on.
you may also want to explore opening your sizing die.....

[gloob]

Thanks for the feedback.

I have put a lot of thought into it. As you can see. And there are definitely some pros and cons to enlarging a die.

I feel like a tight sizing die combo'ed with the requisite expander is good for making high quality ammo in mixed brass. Also, a tighter sizing die can effectively size some cases that might otherwise need to be debulged with a looser cut sizing die. One other possible disadvantage is decreased case life from overworking the cases. I have not found this to be any practical concern, and I feel like overflaring/crimping is more a culprit than tight sizing dies. I have only ever tossed a couple 9mm cases due to cracked mouths, and my 9 die is really tight.

I feel like a looser sizing die and with a flare will be able to make the best quality ammo (via more concentric bullet seating) IF you sort cases, carefully. And you don't have to buy a separate expander. So that is two advantages. But without sorting cases, your ammo might actually be less accurate, and you will have to screen more carefully for thin cases that give dangerously low neck tension.

I just don't feel like you can have a perfect sizing die using mixed brass. You get one problem or the other.

[mongoose33]

I did an experiment last Thursday; normal case expansion for 9mm (normal meaning what I've always done), and then using the .360 expander plug (http://noebulletmolds.com/NV/product_info.php?cPath=89&products_id=1130).

Two things were apparent. One, far less neck tension in the cases expanded using the .360 expander plug, even to the point of bullet setback when the cartridge was stripped from the magazine and fed. Two, absolutely no difference in the smoke generated from the lube.

Now, in fairness I have a couple other expander plugs yet to try, and until I've weighed in with them I'm not drawing any final conclusions. But what was clear was that the boolit was not being resized (I pulled a couple to check), and since that theory was the explanation of why I was getting so much smoke, that theory seems quite in question.

[EDG]

You need to back up and look at the wide range of reloading applications that may be involved in your guidelines.
I get a large giggle when some pistol shooter want to propose his views of reloading on rifle bullet reloading.
One of the reasons is that handgun shooters do not often deal with accuracy in any significant way so they cannot appraise the effect of the changes they make easily. Saying your groups are better at 25 yards with a pistol is not like saying they are better at 400 yards with a benchrest rifle. The handgun shooter rarely has a decent rest of sighting equipment compared to a rifle shooter.

You might think about developing a thing called a decision tree.

The tree asks you a question and the flow chart takes you down a distinct path based on your choices.

It might start out pistol revolver or rifle ammo

Then the rifle branch might say standard chamber or tight bench rest chamber or
maybe choose between cast and jacketed
then chose between tube magazine, box magazine or single shot.

A tight chamber with a jacketed bullet may not even need sizing much less an expander.
Temper and or annealed condition of the brass affects the final diameter due to spring back.
The dimensions of the sizing die has some effect.
The diameter of the bullet affects what size expander is needed.
The length of the bullet shank might affect the expanded diameter.


Revolvers may need a heavy crimp with some loads and little with others.

It is not that simple. Have fun.

[Dragonheart]

I have heard so many times before, "Handguns are not accurate, so it just doesn't make any difference". I say from thousands of rounds of testing with handguns locked into a Ransom Rest that the same attention to detail that makes an accurate load for a rifle can make an accurate load for a handgun. When I have a handgun that can post consecutive 6/10" groups at 25 yards out of a 5" barrel using the same techniques employed in accurate rifle loads, I know that it is the attention to detail that makes a difference.

[EDG]

I think the real problem is most people don't know if a handgun is accurate or not because they really don't have a good way to test it. Few people test a handgun on a benchrest with a scope- unless it is a Contender or XP-100 type singleshot. If you can't or don't have a good means to test your pistols your handloading ideas are basically unproven theories.

Your 6/10" group at 25 yards would only look impressive to another pistol shooter. It is only a 2.4" group at a 100 yards and would not impress many rifle shooters- if you can really get it to maintain that accuracy out to a hundred yards. My point is you can dink with pistol rounds a lot but what you do does not quite translate the same way to a rifle.



I have heard so many times before, "Handguns are not accurate, so it just doesn't make any difference". I say from thousands of rounds of testing with handguns locked into a Ransom Rest that the same attention to detail that makes an accurate load for a rifle can make an accurate load for a handgun. When I have a handgun that can post consecutive 6/10" groups at 25 yards out of a 5" barrel using the same techniques employed in accurate rifle loads, I know that it is the attention to detail that makes a difference.

[gloob]

Mongoose, I dunno what to say. There are quite a few reloaders using the Lee 38SW expander, which measures 356, same as the NOE that you are using. (I have both, in fact). Neck tension is peachy. I take it you are using 356 boolits? I wonder if your sizing die might be a little loose, to begin with.


I think the real problem is most people don't know if a handgun is accurate or not because they really don't have a good way to test it.
The way I test accuracy with a new handgun load is to shoot dirt from 100 yards. At that distance, it's pretty easy to tell when there's a problem with bullet stabilization, just by the size of your pattern. The bullets all exit the bore more or less straight, so it's hard to tell the difference at close range, even on paper.