WD vs HT in a nutshell

[crabo]

Okay, help me to know if I have this figured out. When you waterdrop the boolit gets harder all the way through, but when you size it, you return the outside bearing surfaces to it's original state, but the core stays harder. If you want it to stay hard on the bearing surfaces, you need to size it fairly quick after casting.

If you heat treat, you size first, then heat treat, then lube. This way it is harder all the way through the core and the bearing surfaces stay hard. Then the sizing and lubing is not critical when you do it.

Is this pretty much it? Anything else I need to take into consideration?

Thanks,

[dwtim]

I thought quenching was only surface-hardening.

???

[BABore]

Okay, help me to know if I have this figured out. When you waterdrop the boolit gets harder all the way through, but when you size it, you return the outside bearing surfaces to it's original state, but the core stays harder. If you want it to stay hard on the bearing surfaces, you need to size it fairly quick after casting. The depth of hardening depends on drop temperature and diameter. Boolits, 30 cal and smaller, tend to harden al the way through. 45 cal rifle boolits will typically have a softer core. Again, this all depends on the temp at which you drop it. Your only control is your alloy temp and time. Not near as accurate as OHTing, IMO. If you size WD boolits, within an hour or two after casting, little if any exterior hardness is lost. You can also put them in the freezer to extend or retard that dwell time.

If you heat treat, you size first, then heat treat, then lube. This way it is harder all the way through the core and the bearing surfaces stay hard. Then the sizing and lubing is not critical when you do it. You can size before or after OHT if you want. If done afterwards, your under the same time restraints as WDing. I used to size and check prior to OHT, but had GC's sometimes pop off or loosen on me. Now I size and GC afterwards. You also got to look at your sizing method. I use a push-through, nose-first die set in my Rockchucker. One die body with inserts for diameter. I have lots of compound leverage and don't have to worry about bending a boolit. Normal Lyman/RCBS sizers may give you more problems with hard boolits. I can't detect any difference in final hardness when done before or after. My hardness tester is modeled directly from a Brinell testers 10mm ball/200 kg load setup.

Is this pretty much it? Anything else I need to take into consideration?

Thanks,

How accurate do you need your hardness to be? Water dropping typically will produce more variation in hardness. Everything is based on a precise sequence. Boolits occasionaly stick in the mold or a sprue may cause you fits. Anything that takes you out of the "zone" will cause variation. Oven heat treating is much less susceptable to this. Go from point A (oven) to point B (water) as quick as possible. Any time variation affects the entire batch.

As mentioned above, water dropping can produce boolits that are hard outside, and progressively softer towards the core. This makes for an excellent hunting boolit. You can also duplicate the same thing when oven heat treating. Just use a lower temperature that is close to how they're dropped from the mold. Most books recommend to OHT boolits just below their slump point. This will achieve maximum hardness for the alloy, but there's a big temperature range below that in which to experiment. You can also OHT boolits to their max hardness, then draw them back at different annealing temperatures. A few years ago I ran tests on straight WW alloy. It would OHT to 28 Bhn. I tested annealing temperatures in 25 degree increments. End result was that I could reduce the 28 Bhn hardness in reliable 2 Bhn increments down to 16 Bhn. Very useful in finding a rifle's sweet spot for that particular alloy.

[cbrick]

That's pretty much it Crabo, the only exception I'll take to anything posted so far is that lead, unlike most steels when HT'd hardens all the way through, not just a surface hardening. At least according to the metals industry that’s true.

With time to cool a major factor in HT'ing I've often wondered how much slower the middle of a large caliber bullet might cool and if this could affect the final hardness of the middle. Perhaps, possibly, could be that the center may reach the same final hardness as the outside but with a longer time curve. Dunno; also don't know how a bullet caster could test such a thing. Also have no idea how or if this would be important to cast bullets.

Lead, again unlike steel when worked (sized) will work soften, not harden. So when you size hardened lead you will work soften the driving bands BUT . . . does it only work soften the outside that comes into contact with the die OR does it also work soften the center by virtue of squeezing it in the die? Again, I dunno. Just another of those things that can drive ya nuts thinking about it just because curious minds want to know.

Rick

[BABore]

The trick to getting a soft inner core is the temperature when quenched. You have to be just over the line where it will harden. Cold attracts heat and vise versa. The boolits exterior is closest to the cold where the quench hardens it directly. The boolits heat is drawn outward where it is rapidly cooled. Since the initial temp is just above the point where hardening can occur, the core of the boolit drops below that point before it's rapidly cooled. Only works real well on bigger diameters. To test it you need to shoot boolits into media and compare. A fully hardened (mostly) boolit, that was OHT'd at just below the slump point and quenched, is used as your baseline.

[Marlin Junky]

Only works real well on bigger diameters.

BABore,

Does it work with .35s and .375s?

MJ

[45 2.1]

BABore,

Does it work with .35s and .375s?

MJ

It will work fine on those provided you don't cast too hot. Key is a three to four second sprue freeze and drop into water. The 30 calibers are possible if you have really good temperature and cycling time control.