Heat Treating bullets to increase BHN

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  • Last Post 05 May 2011
billwnr posted this 04 October 2009

Does heat treating bullets (or water quenching) really increase the BHN of a bullet completely, or is it just a surface hardening?

I read the 2nd of the bullet casting annuals from 1994 or 1996 and it was saying that bullets cast of linotype were too brittle to hollowpoint via a HP ram and portions of the bullet noses sheared off.   It said that bullets cast of wheel weights and brought up to the same BHN of lino (BHN 22) and subsequently hollowpointed via the same HP ram “hollowpointed” nicely and didn't shear off.

So, is it just surface hardening??

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Duane Mellenbruch posted this 04 October 2009

No it is not surface hardening.  The hardening effect is throughout the bullet.    Duane

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CB posted this 04 October 2009

Duane

Heat treating of metal by quenching is nothing new. The Romans among others used heat treating in making weapons. Blacksmiths and gunsmiths use quenching to harden metal and for other reasons.

For cast bullet quenching besides attaining a a higher BHN do the bullets perform better once quenched? How do you quench cast and do you quench all your bullets.Thanks.

Stephen Perry

Angeles BR:fire

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Duane Mellenbruch posted this 04 October 2009

Most bullets I shoot are as cast and are determined by the hardness of the alloy used.  Occassionally I have oven heat treated for a specific purpose.  Batch heat treatment provides a more consistant hardness.

Due to the availability of materials, I may need at some point to blend ww and soft lead and heat treat all of those castings in order to provide a harder bullet so it is a good thing to become familiar with the various alloys and characteristics.  Why use Lino for poking holes in paper when a heat treated ww/soft scrap will perform in a similar manner? 

I think you will find different things going on in and on the surface of steel when hardening or quenching those items.  Duane

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CB posted this 04 October 2009

Thanks Duane. I get the feeling that allot here know about water quenching or oven heating bullets but how many go through the process.

Stephen Perry

Angeles BR:fire

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billwnr posted this 04 October 2009

If the quenched bullets are harder than lino, my question is why are they less brittle.

In lead hardness and brittleness seem go to hand in hand.

What's the hardness of a bullet that was quenched to increase BHN, aged for a period, and then sized and lubed?

Doesn't sizing the quenched bullet remove hardness from the areas sized?

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Duane Mellenbruch posted this 05 October 2009

billwnr wrote: If the quenched bullets are harder than lino, my question is why are they less brittle. They contain less antimony.What's the hardness of a bullet that was quenched to increase BHN, aged for a period, and then sized and lubed? That will not be something I can determine because sizing after precipitation hardness begins, stops the process.  It has been recommended that HT or quenched bullets be lubed and sized within 30 minutes of treating.   Sizing the bullet after a longer period of time actually work softens the bullet.  Other sources tell us that Heat Treating or quenching at a specific range of temperatures (420 to 460F) will result in harder bullets.  Hardening occurs rather quickly and then at a point in the future, age softening begins at a slow rate. If you need more information, consider visiting with a metallurgist.   I certainly am not the expert on this topic.  Perhaps others would care to add to this information.  DuaneEdit:  I failed to mention that “Cast Bullets for beginner & expert” addresses heat treating in an article by Tom Gray.  This book is available to CBA members and the price is noted on the inside back cover of the Fouling Shot.  DM

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runfiverun posted this 05 October 2009

duane has it right.

when i water quench i usually only do about 300 at a time so i can go through them and size/check them asap.

the only time i have seen a negative with this is when i have used old ideal checks and had to press them on the boolit

if you can get them to pour out at super close to your sizing diameter you can wait and there is really no issues.

i have gone so far as to quench then back temper the nose for hunting purposes.

just like annealing brass except you don't tip them over.

if i am gonna oven treat them i pour size then oven treat before checking and lubing.

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billwnr posted this 05 October 2009

One thing I need to learn is “heat treating” and “water quenching", while they give similar results, are not synonymous.

One more question for those in the know. If you do water quench and then follow the recommendation to size and lube within 30 minutes, does the water on the bullets affect the lubing of the bullets. I would think the bullets should be dry. Is this a requirement?

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Bob S posted this 05 October 2009

I never used the “water drop” method.  I did try heat treating using the “batch” method: drop on a towel, seat checks and size to desired size, than put'em in the oven for a while and quench in water; run them through a .001 bigger die to lube them just prior to loading.   It definitely made a difference in hardness.  The only “problem” was that the harder bullets didn't result in better scores on the target.  All of my loads had been developed using air-dropped “old” (pre-1970) wheel weights, and these were already shooting Master class scores without any hardening.  I did try pushing the hardened bullets a little faster, but the groups and scores did not improve, and may have even deteriorated some.  Since the extra labor of heat treating didn't “buy” me anything, I quit.  If I ever run out of pre-1970 wheel weights and lino, I may have to revisit the heat treating.  But I have a good supply of both old WW and lino, and my days are numbered, so I'm probably “set".

YMMV .........

 

Resp'y,

Bob S.

USN Distinguished Marksman No. O-067

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RicinYakima posted this 05 October 2009

Bob S,

That has been my experience also. Nothing gained on the target, so it wasn't worth my time. Now, if I just wanted to make a couple of dozen hunting soft points, and increase MV by a few hundred f/s and get expansion, that may be another story.

Ric

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runfiverun posted this 05 October 2009

i dump all mine out on some shop towells and start checking and lubing. with my stars i use a little rod to push each one through after lubing.

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corerf posted this 05 October 2009

Heat treating is to gain velocity, which typically is used to create more energy and a flatter trajectory. It's not going to help with scores on paper. It'll help you get out faster, with “less” leading. If you shoot steel, you need knockdown power. If you shoot pigs, you need penetration. Both are bettered with velocity, which is “typically” improved with quenching or oven treating.

Ric in Yakima said it right.

Treating bullets is about speed, nothing more.

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Dicko posted this 08 November 2009

Agreed, heat treating is to increase velocity, there's no other reason.   Veral Smith looked into it in some depth in his book “Jacketed Bullet Performance with Cast Bullets."   I looked at it myself in a minor way so I'm no authority, but this is what I know for what its worth.

Velocity of cast bullets is limited by leading.   There are various factors in leading or prevention.   Those are velocity, bore smoothness, alloy hardness and lube quality.   Hardness is a material factor.   Pure lead is 5 BHN.   Typical handgun bullets are 12 - 15 BHN.  Linotype ( that's the 4/12 linotype we usually mean ) is 22 BHN.   Lead alloys can be harder, like some of the monotypes with higher antimony content.

The attraction of heat treatment is that it gets high hardness, up to 35 BHN, without the need for a lot of antimony.   However, the seldom mentioned glitch is that it needs arsenic.   Not just any amount but about 0.25%.   Much less doesn't get results and much more results in embrittlement and possible bullet fracture.   In the past wheelweights have heat treated successfully because they contained just the right amount of arsenic.   Don't know whether that can still be relied on, but there used to be a specification of 0.50% tin and 4% antimony, and I can tell you that wheelweights don't meet that spec these days in my part of the world.

There is no guarantee that any other alloy will contain the right amount of arsenic, and the only way you can guarantee that is to blend your own from virgin materials.

Antimonial alloy work softens, so yes, sizing a heat treated bullet can be expected to soften it.   The answer is to size them before heat treating them.

My feeling is that it just ain't worth the trouble.   Rather stick to a good alloy you blend yourself and ensure consistent hardness that way.   Bullets cast with enough antimony for rifles are still dirt cheap compared with jacketed, and the cost of a decently hard bullet is not much more than one that's too soft.

If we want to keep our cast bullets economical the best place to look is the high cost of gas checks.  

 

 

 

 

 

 

 

  

 

 

 

 

 

 

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CB posted this 08 November 2009

I'm continually amazed at how complicated people want to make all of this. I've been oven treating and quenching from the mould for years and never thought much about it. If you're worried about arsenic throw a little magnum shot into the mix. Need some tin? Put a bit in. I've never measured anything and it always heat treats to about the same BNH, 19 from the mould and 35 or so from the oven.

Size before or after oven treating and by neccesity after if you quench, doesn't make that much if any difference. You don't have to wait for more than about 12 hrs for the HTing to complete but if you want to sit around for 5 years waiting to shoot the things that's up to you. Why worry about age softening? If you plan on casting a pile that's going to last the rest of your life just don't lube or install the check before you send them for a trip through the oven and problem's solved.

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Dicko posted this 09 November 2009

There you go.   I said I'm no authority so I accept this.   Seems simple enough for anyone to try.   Personally I don't see the point but then I'm happy sending cast bullets down range from my 308 Win at 1400 FPS in front of ten grains of MP200 (similar to Unique).   For that 10% antimony makes 'em hard enough as cast.   No gas check and no leading.

I have tested gas checked up to 2400 FPS.   Still no leading but I can't vouch for accuracy yet.    But I'd be the first to agree that if you want to push MV without gas checks the harder you can make 'em the better, and heat treating helps with that.

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billglaze posted this 01 May 2011

Please understand: I am not arguing or differing with any opinions expressed here. Just putting out my experience for others to reply to. I find this whole thread highly interesting. I have the latest (#4) Lyman Cast Bullet Handbook, in which a man who has the crerdentials, (PhD in metallurgy, as well as more letters also)cogently states that heat treating, (or, age hardening) does little or no good for hardening lead alloy. Yet, until I got Veral's book, (many years ago) and started oven-hardening bullets, I was having between little and no luck whatsoever obtaining accuracy--at any velocity. Inasmuch as it seems the hardening (I routinely obtain BHN of 32 casting with nothing but WW's) should go completely throughout the bullet, I find that sizing after treating does not seem to affect the brinnell. And, Veral wrote me that it was O.K. to size after oven-baking. I really don't care about trajectory, because I only shoot holes in paper, and at a known distance. I am, however, trying for the best groups possible with the given rifles/ammo/shooter. Any discussion?

In theory, there's no difference between theory and practice. In practice, there is. My fate is not entirely in Gods hands, if I have a weapon in mine.

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RicinYakima posted this 01 May 2011

Discussion? Well, in my opinion, measured BHn of the bullet has little or nothing to do with accuracy. The alloy only has to have enough strength for the design of the front driving band to begin bullet rotation, without grossly pushing metal back into the top groove. Accuracy is related to the bullet's fit of the throat, leade and bore, and how concentric the bullet is with the bore when the cartridge is ignited.

I haven't read a copy of new #4 so can not comment on what is his opinion on heat-treating, age hardening vis-a-vis what?

Ric

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pat i. posted this 02 May 2011

billglaze wrote: I have the latest (#4) Lyman Cast Bullet Handbook, in which a man who has the crerdentials, (PhD in metallurgy, as well as more letters also)cogently states that heat treating, (or, age hardening) does little or no good for hardening lead alloy.  

I haven't read the article but if the guy's saying that HTing wheel weights, a lead alloy last time I checked, doesn't make them harder I congently state he doesn't know his arse from a whole in the wall no matter how many letters he has after his name. But like I said I haven't read the article.

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Dicko posted this 03 May 2011

The hardening agent in non heatreated cast bullets is antimony. But antimony is a very brittle material, and linotype bullets (12% antimony) have been known to fragment on game. Pure lead is ductile and will deform considerably while holding together. So its a trade off for cast hunting bullets. 6% Antimony will expand and hold together quite nicely while being good for over 2000FPS with as check.

Quench hardened bullets can be as hard as 35 Brinell, compared with 22 for linotype. So why are they less brittle ? Because they contain less antimony. They are therefore very useful for hunting.

Antimonial alloys work soften. The old lead water pipes were usually 6% antimony, but felt soft and marked easily with a thumb nail, like pure lead, because they were softened by the extrusion process. The soft pipe casts into hard bullets. Consequently, sizing could soften bullets whether heat treated or not, but in fact the small amount of sizing seems not to soften them significantly. But, for heat treated rifle bullets, it makes sense to heat treat them before sizing.

Does anyone remember Lyman's two piece bullet of years ago ? It was a semi wadcutter as I recall. The shank was cast from linotype and the nose from pure lead. The two parts were joined by a sort of spigot and socket joint. The shank had a 60 degree conical recess, and the nose a matching cone. They were glued together with two part epoxy. The only purpose must have been for defense loads, because making 'em must have been too much work for range use. But it clearly demonstrates the point about hard alloy for velocity and pure lead for expansion and weight retention.

How reliable is Lyman's #4 Handbook as a manual of bullet casting if it can publish that heat treatment does nothing for bullet hardness, when we all know otherwise ? An earlier edition (forget which) said that tin can separate out of the alloy (wrong) and elsewhere in the same book that it can't (right). Go figure.

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James Ball posted this 04 May 2011

back some 30yrs ago while working in a foundry i found,they brought metal hardness up by puting metal parts in alcohol and dry ice for 20-40 min.get it below zero temp.James Ball

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Mnshooter posted this 04 May 2011

Heat treating bullets does have certain other uses. For a target shooter some claim a heavier bullet can be used than with linotype which has some advantages. I use them a lot as I use a soft alloy about 1-1 lead/WW or 2-1 lead/WW. I heat treat and then place the base of the bullets in a water pan and anneal the noses. They make a hunting bullet that performs like a Nosler. I ahve had excellent results with this method on deer and shoot them accurately at about 2000 fps.

DP

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billglaze posted this 05 May 2011

Sorry taking so long to get back, but what Dr. Block seems to compare to is either linotype metal, or something similarly hard. (I'm going to read the entire thing again, starting tonight.) In any event, I haven't seen any linotype for many years, so I have to make do with WW. And, I realize that I'll never be in the realm of 1/2” groups, and such esoterica, but I would like to at least be able to use the more easily obtainable (read: Cheap) sources, while gaining acceptable accuracy. (1 min.+/-) Rght now, I have, for the first time, started using Red Rooster lube, that the company owner gave me at the 1987 N.R.A. Convention.(!) I am looking to see if it makes a difference. I agree that the factors you mention are important, but if for one reason or another, you aren't delivering a well cast, perfect bullet to the outside world when shooting them, you aren't going to attain the necessary consistency. In any event, I have continually reduced the powder charge/velocity until I'm shooting in the 1400's. I'm now wondering if a GC is even necessary at that level. And, we'll see if the Red Rooster helps. So far, when below 2000 fps., (+/-) what leading I've been getting are just a very few (like 2 or 3) tiny sparkly specks on the patch when swabbing out the barrel. This is with the Lyman/Alox, which is all I've used for years. I'll see. And the beat goes on.

In theory, there's no difference between theory and practice. In practice, there is. My fate is not entirely in Gods hands, if I have a weapon in mine.

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