What is the difference between swaged and sized?

I load thousands of bullets but don't cast any of my own. I was just curios because I always thought the swaged were supposed to be more accurate but since the earlier post about 32 HBWC I have been trying to wrap my mind around the difference. Ok, swaged you take a known amount of cold lead/mix and squeeze it until you have a bullet the shape, size and weight you want. Sized you take a bullet of known weight, size and shape and squeeze it until it is the diameter you want. Both processes are done when the lead/mix is cold. Why would one be more accurate then the other? Magnus sizes my bullets (that I order from him) down from the 130gr .358 to a 130gr .356 and they look like the swaged bullets I get from him for my 52. How am I thinking about this wrong? Thanks for your thoughts.

Len

I think of a swaged bullet as one that is soft lead (possibly wire) compressed from all sides to form the bullet and because of that should not have any defects or voids in it.

A cast bullet being molten lead poured into a mold then passed through a sizing die squeezing only the sides, in this process the bullet can have voids that are unseen or defects on the base that will still be present after sizing.

I suppose you could just size a swaged bullet and then there really wouldn't be much of a difference, if any.

Kurt

what Kurt said.

biggest difference is hard (cast) vs. soft (swaged).

What did Hershel shoot?

Lead Metallurgy is really odd.  

For swaged Lead bullets one will often use nearly pure Lead, which is really soft, but has a much higher melting temperature than much of the Lead scrap that is around, because common alloying elements like Tin in the scrap usually sharply depress the melting temperature.  There should not be any voids in a swaged Lead bullet.  

The OP speaks of sized Lead bullets.  What I believe he is referring to is cast Lead bullets, which usually are sized after casting.  There are a very few materials which expand on freezing, so usually do not have porosity due to shrinkage in volume between the liquid phase and the solid, and Lead and its alloys are not one of them.  Virtually any Lead you use to cast a bullet is going to be an alloy, Lead scraps having Tin, Antimony, Arsenic, and other things in them.  If you want to envision how virtually any alloy freezes, it does not happen as a smooth front passing through the pool of liquid, it happens through tree-like 'dendrites' growing into the pool of liquid.  At first, the spaces between the branches are large enough that liquid can move to fill in what would otherwise be a void, but this becomes harder as more an more branches grow into the pool.  Eventually more liquid can not flow in, and further solidification volume reduction will cause a void.  At U of M in our casting classes, we spent a lot of time designing molds with insulated areas to slow freezing, risers to supply liquid metal to fill in the voids, and gating channels to supply more liquid to more places, but we can't do much of that in Lead pistol bullet molds.  You want shrinkage voids to be very fine if possible.  

The weirdest thing about Lead is what happens when you resize it.  Something that happens with all metals is 'Recrystallization'.  It happens at about half of the melting temperature of a metal, expressed in degrees absolute.  For Lead, that is right at room temperature.  When metals recrystallize, they spontaneously reorganize themselves.  This recrystallization always reduces hardness.  The typical piece of metal which has been cast, cold worked or machined to a shape has lots of stresses and strains locked into the zillions of little crystals that make it up.  Those stresses are what power the recrystallization.  Sizing is a cold working process.  Because it can cause recrystallization, cold working can cause a softer, not a harder bullet.  

A cast bullet does not have to be sized, if it drops from the mold at the right diameter.  I used to attend a lot of Bowling Pin matches, and most of the .40 and .44 bullets I shot at them were cast at an acceptable diameter, and dip lubed.  The lube I used was Lee Liquid Alox, a product of the Lubrizol Corporation, which bought out the Alox Corp, and is Lubrizol's 606-55, a viscous liquid.  

NRA testing many years ago showed that an as-cast bullet always shot better in pistols than a sized one, and the more sizing done on a bullet, the worse it shot.  

There is another Alox compound in bullet lubricants, 50% Alox 2138F mixed with 50% Beeswax, to produce an excellent but smoky grease-type lube.  This lube is made by many vendors, and is most frequently referred to as "NRA formula" or "50/50" lube.  I apply this lube through lubricator/sizer machines.

Thanks everyone for their answers. I think I got most of my answers. I was impressed with Nujudge answers on recrystallization. I thought (wrongfully) that when a bullet was resized (crimped smaller) that the new bullet would be harder. Apparently the reason they feel like a swaged bullet is because they are softer after the re-sizing.  the resized bullets Magnus does for me were cast for a 38/357 and I have them sized for a 38 Super. I guess I will just shoot them and quit worrying about the physics.

Len

Just for information:
Hornady uses 95/5 or 94/6 lead alloy of swaged bullets and Precision Bullets uses 92/6/2 alloy. They really are not soft, just not 18-22 BHN.
However, if you need 18-22 BHN, they could certainly swage the bullet for you.
Aren't monolithic bullets swaged and then the grooves machined to cut down on pressure?
Swaging, for bullets, implies the lead is placed in a mold and pressure cold swages the lead to the bullet form. Weight and dimensions are tightly controlled. Same process used for jacketed bullets.
The main thing is you can't swaged lube or crimp grooves, so they have a cannelure to hold more of the wax emulsion that is generally used. Zero has a band of what looks like Carnauba Red around a strip of the driving band.
Swaging is also passing a tube/rod through a die and swaging it down in diameter. We did a lot of that in the wire & cable industry.
Technically, one could argue that sizing a bullet is a swaging operation, but it doesn't give you a "swaged" bullet.