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Discussion Starter · #1 ·
I've been reloading .45 ACP brass for a few years on an RCBS carbide sizing die. But I've begun wondering why it's necessary, since the case is not necked down. My brass isn't deformed and I have never trimmed the case length. Since my decapper die is also my mouth expander die, wouldn't that also take any deformity out of the "tube" shape of the case if needed? Just curious to see what more experienced reloader think (it is a pretty labor intensive process on my single stage press to "size" cases that look the right size already). Thanks.
 

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The case expands when fired, so it usually needs to be sized back down for a couple of reasons. Fired cases don't always fit back into the chamber that they were fired it. And if they are not resized they might not have sufficient tension to hold onto the bullet when it it seated, resulting in the bullet being pushed back into the case when it feeds (setback).
 

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Discussion Starter · #3 ·
The case expands when fired, so it usually needs to be sized back down for a couple of reasons. Fired cases don't always fit back into the chamber that they were fired it. And if they are not resized they might not have sufficient tension to hold onto the bullet when it it seated, resulting in the bullet being pushed back into the case when it feeds (setback).
Yes, it makes sense. I suppose I should measure the case diameter before and after resizing just to learn how much "sizing" really takes place. I understand that chamber tolerances are tight, even if it's not possible to visually see the difference before/after going through the sizer. Thanks for the explanation.
 

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Bless ya, Jerry, you need to go back and review your loading manuals.

Look at the SAAMI chamber dimensions and cartridge dimensions on their web site.

Notice that the chamber is larger than the cartridge. Like superdude says,
the brass expands. Thus, used brass is larger than a new cartridge.


You need to size the brass back down so it holds the bullet.
Go ahead, expand and seat bullet in a few cases, then crimp normally
(but without primer and powder). Put them in a magazine and
pull back the slide and release to chamber the rounds one after another.

Upon withdrawing the cartridges and look to see if the bullets stayed in place.
 

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Because re-sizing the case is the only practical and efficient way to “restore” the correct case “dimensions” and case “tension” back to the fired brass case.
There is no other “simpler” or more “efficient” way to do this in a uniform manner.

You really can’t blame the “process” on the laborious nature of your loading, this is due to your choice in Handloading equipment.
With your single stage configuration you have to handle and process each case a minimum of three times to complete a cartridge assembly, four times if you add a separate crimping stage.

If you were loading on a multi-stage progressive, after loading at all stages once, you would then only handle a case once and complete a finished cartridge for every once handled case processed on the press.

:)
 

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Remember, case sizing is what holds your bullet securely in a .45 ACP round (not crimp).

Nick mentioned this (and others) but it bears repeating. :)
 

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Discussion Starter · #7 ·
Bless ya, Jerry, you need to go back and review your loading manuals.

Look at the SAAMI chamber dimensions and cartridge dimensions on their web site.

Notice that the chamber is larger than the cartridge. Like superdude says,
the brass expands. Thus, used brass is larger than a new cartridge.


You need to size the brass back down so it holds the bullet.
Go ahead, expand and seat bullet in a few cases, then crimp normally
(but without primer and powder). Put them in a magazine and
pull back the slide and release to chamber the rounds one after another.

Upon withdrawing the cartridges and look to see if the bullets stayed in place.
I'm not arguing with any of you far more experienced reloaders. I've always reloaded by the book - I don't want any misfires/squibs/etc. But I guess up to now, I've reloaded by rote, without thinking too much about the theory. For example, in a match chamber, I imagine the case "just" fits, and when the spent case is extracted from the chamber it comes out easily enough (so it's still the same diameter as when it went in, or it would get stuck?). Does that mean the case expansion takes place as the hot case is cooling after ejection? Or is there "just" enough space between the outer case wall and the chamber wall to allow for expansion without causing a case to stick in the chamber? I'm using this thread to learn the theory behind the process I've used up to now. Thanks again for the expertise.
 

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Discussion Starter · #8 ·
Because re-sizing the case is the only practical and efficient way to “restore” the correct case “dimensions” and case “tension” back to the fired brass case.
There is no other “simpler” or more “efficient” way to do this in a uniform manner.

You really can’t blame the “process” on the laborious nature of your loading, this is due to your choice in Handloading equipment.
With your single stage configuration you have to handle and process each case a minimum of three times to complete a cartridge assembly, four times if you add a separate crimping stage.

If you were loading on a multi-stage progressive, after loading at all stages once, you would then only handle a case once and complete a finished cartridge for every once handled case processed on the press.

:)
OK, I never thought of restoring case "tension" before, just size. And I'm OK with the single stage process - it makes me go slow and careful, even if my arm gets tired doing a few hundred "sizing" pulls on the press at a time. And I think it helps me shoot with more care, since I'm not knocking out rounds anywhere near fast - just slow and careful - so I shoot with the knowledge of how much work goes into making each cartridge. Thanks for the info.
 

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Your decap pin should be set up in your sizing die,not the expanding die.That is unless RCBS changed things.

Do you batch reload?It seems to go quicker.I only use loading blocks holding a charged case,other than that my brass stays in plastic bins like large butter containers.I pull brass from one bucket and put it in an empty one until they're done,if I can continue I do or I throw the lid back on until next time.If I have time,I run through deprime and size,swap the buckets and flare and reprime.Next time I charge and seat a bullet and then crimp them all,breaks up the monotony in 2 sittings but you can go 3 or 4 if time is scarce.
 

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Jerry, you're a good curious handloader. In addition to what we can tell you here,
you'll learn 1000 times more in the manufacturers' written resources.

I particularly like the way Hornady wrote up their tutorials, but Sierra and
a host of others also have excellent descriptions.


The case must be several thousandths of an inch smaller than the chamber
(even match chambers) or the loaded cartridge won't go in smoothly,
in fact it won't chamber at all in many instances. [Note: Many match chambers
are not tight, they are loose for fast action, especially IPSC type guns.
Those chambers are match grade because they align precisely with centerline
of bore and centerline of firing pin tunnel. Tightness does not always mean
super accuracy, all the dimensions must add up and line up for match accuracy.]

OK, so the cartridge must be loose to go into the chamber. Being loose,
hot gas would blow back at the shooter every time the powder discharges.
But cases are made from soft materials like brass, or aluminum, or soft steel
so they expand to seal the chamber as the pressure builds. In fact, the case
expands to seal the chamber before the bullet leaves the chamber.
That is the expansion we're talking about. As the powder burns and pressure builds.
As the bullet travels down the bore, pressure begins to subside.
As pressure lets off, the brass shrinks down a half a thousandth of an inch.
Not back to its original dimension, just slightly. At that point, it is
easier to extract. The slide/bolt/whatever action you have moves backward
and the brass is extracted, already expanded beyond original dimension.

Thus, you need to 'resize' to get it back to original dimension.

That's why that step is called 'resizing'. It returns it to original size.




The notion of resizing brass, case tension holding the bullet, and
expansion of the brass in the chamber are very basic to ammunition,
ballistics and reloading. I really encourage you to get excited about
finding and building a library of resources for your education.

:)

The science of what happens inside the chamber and the bullet inside the bore
is called Internal Ballistics. Hornady has a particularly good write up about it.
Go seek it out!
 

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Your decap pin should be set up in your sizing die,not the expanding die.
Decapping in the expanding operation is the original way of doing it
from early in the last century (early 1900's) until about 1970 or so.
That's when they started switching the decap pin to the resizing die.

Several of my old pistol die sets (380 auto, etc) don't even have an expander.
There is a resizing die, a decapping die, and a seating die (3-Die Set),
or just a resizing die with decapping pin, and a seating die (2-Die Set).
RCBS, Herters, Lyman and others were all on that same trip back then.

The industry pretty much got its act together now. Good thing!
 

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[Note: Many match chambers
are not tight, they are loose for fast action, especially IPSC type guns.
Those chambers are match grade because they align precisely with centerline
of bore and centerline of firing pin tunnel. Tightness does not always mean
super accuracy, all the dimensions must add up and line up for match accuracy.]
How does an off-center firing pin strike affect mechanical accuracy? How far does firing pin alignment need to be to affect accuracy in a 1911? .005", .010"? More, Less? And how much does that increase group size? Surely, this must have been tested and documented and you are referring to published data or you would not say this. Do you have that reference? I'd like to learn more about this.
 

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How does an off-center firing pin strike affect mechanical accuracy? How far does firing pin alignment need to be to affect accuracy in a 1911? .005", .010"? More, Less? And how much does that increase group size? Surely, this must have been tested and documented and you are referring to published data or you would not say this. Do you have that reference? I'd like to learn more about this.
No, it doesn't as far as I know. But you just like to challenge me at every turn, don't you?

The smiths who make those guns align firing pin tunnel for reliability.
You know that.

Instead of challenging me all the time, just correct me when I make a boo boo.
I take correction perfectly well. I'm a nice fellow. :) I don't fight back.

And it makes you look less confrontational too. :D Big grin.
 

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I've been reloading .45 ACP brass for a few years on an RCBS carbide sizing die. But I've begun wondering why it's necessary, since the case is not necked down. My brass isn't deformed and I have never trimmed the case length. Since my decapper die is also my mouth expander die, wouldn't that also take any deformity out of the "tube" shape of the case if needed? Just curious to see what more experienced reloader think (it is a pretty labor intensive process on my single stage press to "size" cases that look the right size already). Thanks.
The case can balloon as it is ejected, still under pressure. It won't necessarily go back into a chamber freely. You need to restore uniformity to ensure reliable function. Sizing will give you this.

Your frustration with the task makes you a prime prospect for a turret press.
 

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Pictorial says it all:

First photo is an UNsized 45 acp case dropped into a Wilson case gage. Brass has been cleaned but not yet sized.



This photo is of a SIZED (and primed) 45 acp case dropped into the Wilson gage.

 

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I've been reloading .45 ACP brass for a few years on an RCBS carbide sizing die. But I've begun wondering why it's necessary, since the case is not necked down. My brass isn't deformed and I have never trimmed the case length. Since my decapper die is also my mouth expander die, wouldn't that also take any deformity out of the "tube" shape of the case if needed? Just curious to see what more experienced reloader think (it is a pretty labor intensive process on my single stage press to "size" cases that look the right size already). Thanks.
It's unfathomable to me that somebody who's been reloading "for a few years" would think that the reason he uses a sizing die is to "correct deformities." :eek:

Rx:

 

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In addition to needing to re-size pistol brass (I do 9mm, .45 and 380) so the bullet doesn't just drop down into the case when in the bullet seating die, since i re-use pick-up brass from our weekly indoor IDPA shooting, often shot in large chamber guns, i need to take out the slight bulge near the case rim.

I still find about 5% or so of my LNL reloaded 9mm won't quite drop into a Wilson case gage. They still chamber in my 1911 and High Power pistols, but i put them aside for my own range practice, and don't use them in competition. If I shoot a box of my "seconds" at my LGS's indoor range, i leave them on the floor, so I don't keep having to separate them over and over when i reload.

All the best....
 

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Decapping in the expanding operation is the original way of doing it
from early in the last century (early 1900's) until about 1970 or so.
That's when they started switching the decap pin to the resizing die.

Several of my old pistol die sets (380 auto, etc) don't even have an expander.
There is a resizing die, a decapping die, and a seating die (3-Die Set),
or just a resizing die with decapping pin, and a seating die (2-Die Set).
RCBS, Herters, Lyman and others were all on that same trip back then.

The industry pretty much got its act together now. Good thing!
I'll be,I did not know that so thanks Nick.

I didn't get into reloading until sometime in the 80s as you can tell.
 

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Your decap pin should be set up in your sizing die,not the expanding die.That is unless RCBS changed things..


Things were not always as they are now. This is a 44 Magnum RCBS expander/decapping die from earlier years. I generally use it for 44 Special these days but have to remove the decapping parts to allow it to go deeply enough into the shorter case.

I like the new setup with the carbide sizing dies much better. The only problem I have had with the carbide dies is with 357 Magnum cases that get a slight bulge near the base from a loose chamber. They would not chamber easily in a rifle with a tight chamber. The carbide die does not size down as far as the old steel die. I either run all my 357 Magnum cases through both sizing dies or just lube the cases and use the old dies to take care of this problem.
 

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Jerry, you're a good curious handloader. In addition to what we can tell you here,
you'll learn 1000 times more in the manufacturers' written resources.
I bet you would learn more by giving your idea a shot. Then any problems that pop up will be a good lesson on the "why" part of your question.


Most rifle dies still have the expander and decapping pin in the size die.
 
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