Okay, another stupid question

358156 hp

At large, whereabouts unknown.
I think most of us are familiar enough with controlled heat-treating to achieve various bullet hardness goals, but I'm wondering if a partial quench on a temperature acclimated bullet could result in a hardness gradient with longer bullets. Specifically, if you heat your cast bullets in a controlled environment (okay, a temp controlled oven), then set them base first in a container of chilled water that only covers perhaps 1/4 or less of the bullets overall length, would the bullet possibly exhibit more hardness at the chilled base than at the nose, which wouldn't receive any direct quenching at all. I think you see where this is going, it's almost the reverse of the annoying procedure of annealing bullet noses to make soft points. The top portion of the bullet would cool at a slower rate, and potentially not be as hard as the base.

I would think that a long bullet design would be necessary so as to keep the two temperature extremes as far apart as possible. I can also think of things that could potentially go wrong with this as well, not the least of which would be that any difference between the nose and base hardness could be negligible. The fragility of a cast bullet fresh from the oven just above its slump point hasn't escaped me either, but I haven't posted anything really stupid here for awhile and though I'd throw this out for everyones amusement.
 

Ian

Notorious member
You interest me exceedingly. If this worked it would be the solution to some challenges of my own. It would be easy enough to test with pliers and one bullet, and I'll do so next chance I get.

One thing I do know is that the core of a heat-treated/rapidly-quenched .45-caliber bullet will be several bhn points more soft than the "skin".
 

Brad

Benevolent Overlord and site owner
Staff member
I can see what you are after. For the few bullets needed for hunting the diddly nature of doing this wouldn't matter.
Interesting concept. Try some that way and some water quenched fully and see how they react on impact?
 

Rick

Moderator
Staff member
One thing I do know is that the core of a heat-treated/rapidly-quenched .45-caliber bullet will be several bhn points more soft than the "skin".

Not according to the metals industry, it may take a little more time for the center but the bullet will be the same hardness all the way through.
.
 

LongPoint

Member
I did the exact thing you are talking about on 10-06-14 just to see. I cast up a couple hundred 311041 bullets from 50/50 WW/pure with about 2% tin added, air cooled. I set the wifes oven to 425 degrees and let 2 batches in separate wire baskets soak for 1 hour. The baskets hold the bullets base down. I rigged a pot with 4 little spacers to keep the basket off the bottom and filled the pot with cold water to cover the bottom one third or so of the bullets. After the soak, one basket went into the pot and the other went into the sink full of cold water. A few days later I took one of each batch and put them nose to nose in an RCBS .313 sizer die without the pushrod. I put the test bullet contraption in a small bench vise and squeezed slowly while rotating the die so I could feel if/when some base expansion had happened. As I recall the die never did bind up with the force I put on it in the vise but there was quite a bit of difference in the nose diameter of the test subjects. I never did shoot any of them and still have the remainder of the test bullets. Would probably be great for thin skinned game and such.
Marvin
 

Intheshop

Banned
Interesting....first thing that popped into my pea brain was...

When casting pace gets a little fast,I touch the sprue hump with a damp rag before smacking it open.These are water quenched so while it prolly don't amt to much....it may if they are dropped normally?
 

LongPoint

Member
Well its raining here today so no work for carpenters. I went to the garage to mash some more bullets and take measurements. I used the leftover bullets I spoke of in my last post in the .313 sizer die and the bench vise. I took the measurements 90 degrees from the parting lines. A full quenched (wd) bullet was used in the die nose to nose with a bullet that had only the bottom 1/3 or so quenched(sp). Heres what I got. All bullets had been sized and GC's seated in a .311 die back in 10-06-14.

Meplat, Front Band, Start Of Ogive, Base Band, Length

Just enough pressure to get some change
WD .243 .3105 .3014 .3112 .983
SP .261 .3105 .3015 .3112 .970
Heavier pressure
WD .297 .3108 .302 .3127 .944
SP .310 .3113 .303 .3131 .930
There is some misalignment of the bullets in the .313 sizer die so the nose does not upset evenly so I popped the GC's off a couple and did the test base to base.
WD .257 .3108 .302 .3112 .938
SP .272 .311 .303 .3125 .918

Next I used one of the SP bullets nose to nose with a 311041 cast of WW plus 2% tin, AC

WW AC .256 .3112 .3024 .3123 .964
SP .238 .3105 .3016 .3127 .989

Well thats it folks
Marvin
 
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Ian

Notorious member
Not according to the metals industry, it may take a little more time for the center but the bullet will be the same hardness all the way through.
.

I knew you'd be along to repeat that, but at my house it isn't so, unless "a little more time" means a decade or more. Must be an etherial vortex in the Texas Hill Country or something.

I've very encouraged by Marvin's tests, it looks like the hardening can be controlled lengthwise as well as outside-in. I'm definitely going to try this with my 230-grain .30 caliber bullets and also my 500-grain .458" bullets and check hardness over time with the Lee Brinell tester.
 

Rick

Moderator
Staff member
Well I guess your testing methods surpass that of the metals industry but as long as your happy with your results all is good.
 

fiver

Well-Known Member
hmm.
I need to probably build a powder coat rack for standing up the tall boolits to cook in the oven anyway.
i'll put this in the memory bank.
but it should be easy enough to lower that rack into a pan with just enough ice water to cover the drive bands.
I just haven't got to needing any tall boolits powder coated yet.
 

358156 hp

At large, whereabouts unknown.
I think I'll use my elderly Ideal 358429 SC for my trials. I plan to cast & cool the test bullets, then file a flat down the side to make hardness testing more reliable before trying the actual heat-treating. This will give me a base line, plus allow testing hardness at the base, a midpoint, and the nose. The only thing I really need is the time to do it. I'll use the guidelines in Ricks articles on heat-treating to track the progress of the hardening. I have to use my world-famous "mutt" alloy (scrap) but I still feel any results will still have enough validity for me to decide if I continue with the project.
 

Rick

Moderator
Staff member
According to Veral at LBT filing the bullet will give erroneous results via work softening the alloy. I've not tested this myself but it sounds logical.
 

Brad

Benevolent Overlord and site owner
Staff member
What happens if you file a flat before heat treating? No chance of work softening.

I think of this a little like tempering a knife. Get the base real hard but because you used maybe 1/8" of water the heat treat hardness decreases as you get away from the base. With an inch long bullet you might get a 18BHn base and a 12 BHn nose.

Proof lies in seeing if a partially hardened bullet behaves differently from a fully hardened one on impact.
 

Ian

Notorious member
I plan to cast & cool the test bullets, then file a flat down the side to make hardness testing more reliable before trying the actual heat-treating.

Good idea, I may do the same.

I received some criticism on my test methods because I sawed the bullets in half. There may be some change due to the smearing of alloy, but to check core hardness I don't know how else you'd do it. I checked the cores in three places lengthwise and both sides near the edge in three places adjacent to the center test points. There was no distortion of the outer test marks due to being near the edge, and in fact they tested harder than the core. IIRC this was quite a few months after the bullets were cast, and they were only water-quenched from the mould, not re-heated in the oven for maximum surface hardness.
 

popper

Well-Known Member
200gr. 30 cal has ~ 10 BTU @ 400F, losses 4 BTU every 10 sec. to ice water. It is the rate of cooling that gives hardness by 'freezing' the alloy from inside out. I know, sounds funny but. The temp from inside to outside is only a few degrees so very little difference in hardness from outside to inside. Quenching happens so fast it is difficult to control from nose to base. Lead conducts heat very rapidly.
 

S Mac

Sept. 10, 2021 Steve left us. You are missed.
Looks like to me you could pour the nose with soft lead, the harder lead for the base, heat treat and quench and maintain the soft nose.
 

Ian

Notorious member
Here's a good takeaway from the Beartooth article, and 75/25 WW/soft scrap alloy will do the trick nicely:

"The third and most important thing is that the data show this method will produce a bullet with a BHN of 8-13 on the nose portion and a BHN of 23 on the aft portion using a very simple technique not much more complicated than the full-quench treatment described by Dennis Marshall, so long as an alloy is used that will quench harden to 22-24 BHN and normally age harden to between 8-13 BHN."
 

Chris

Well-Known Member
here's another one. The mix of magnum shot and 5% tin may seem unusual to some, but it provides a hardenable alloy that is ductile enough to expand and yet retain base hardness. You can see the nose change hue a tad and remove the heat. I think it is practical and have hunted with these bullets, but keep in mind the nose hardness can never become lower than the base alloy BHN as cast and air cooled.

http://www.leverguns.com/articles/paco/358_wcf.htm

Here is the pertinent quote from the interesting article on .358 Winchester. I hope Mr. Kelley doesn't mind the fair use excerpt:

"Lyman’s 3589, is the original mold number...not sure what it is today, probably something like 358009. But it is a round nose at around 280 grains in weight. I cast these bullets from magnum shotgun shot with 5% tin added...cast hot and dropped directly into water.

The ones I’m going to use for hunting I size and lube...then place them standing in water up to just above the shoulder and run the butane torch over the noses ...doesn’t take much...at the first sign of color change take the flame off...Let them cool slowly and the temper in the noses is gone for good expansion ...yet the body is hard and will take high pressure and velocity without fouling....pushing these from the 358 Winchester cartridge at 2400 fps is a snap with H335, AA 2015, or 3031...accuracy is very fine. Muzzle energy is almost 3600 lbs....a 30-06 has to work very hard to get even close to that kind of power."