BHN vs alloy composition

Brad

Administrator
Staff member
A frequent area of confusion is the use of BHn to compare alloys. While BHn gives us an indication of one physical attribute of our bullets it doesn’t really tell the whole story.

Case in point. I can cast a bullet from straight Linotype and get a 22 BHn bullet. I can also cast a bullet from a far lower Sb, and lower yet Sn alloy then heat treat it. I can get the same 22 BHn this way.

Those bullets will behave in a far different manner in the gun and on target. The Linotype bullet will be brittle and prone to fracture. The “lower” alloy will flow rather than break. It will be far better for hunting.

How about a nice discussion on alloy and heat treating and how BHn doesn’t tell the whole story.
 

Gary

SE Kansas
I'd love to contribute to a conversation on this subject, but my Alchemy Foo is a bit rusty. :) Organic and Inorganic chem was over 45 years ago, I'm doing good to remember my SS #.
 

RicinYakima

High Steppes of Eastern Washington
How about a nice discussion on alloy and heat treating and how BHn doesn’t tell the whole story.
Brad,
For me, BHn doesn't tell any of the story. I have cast as much linotype as any other alloy. The only time hardness matters to me is for self loading pistols so the bullets don't get deformed on the feed ramp. What I needed though, each season, was 2500 as close to perfect and exactly the same (0.25%) weight bullets, and linotype and half and half monotype and WW's have the lowest cull rates.

For my varmint and vermin control shooting, something like 94/3/1 with a gas checked and hollow pointed bullet was effective and leading free from the 25/20, 32/20 and 357. The little heat treating I have done is with the 30/06 for heavy bullets for deer and bear hunting. The bullet, in my opinion, should have enough malleability to flow and not break. The heat treatment is only to get them out the barrel without slumping, sagging or getting deformed and loosing accuracy enough to wound the game or miss.

Ric
 

Ian

Notorious member
The bullet, in my opinion, should have enough malleability to flow and not break. The heat treatment is only to get them out the barrel without slumping, sagging or getting deformed and loosing accuracy enough to wound the game or miss.
That's exactly how I think of it too, except not as "short and sweet".

Regarding abrasion resistance and initial compressive strength, a watered-down but heat-treated bullet will behave in similar fashion to one alloyed up to the same bhn but it will eventually fail under large compressive force (like smacking a deer or in some cases being punched too hard with a powder that's too fast), whereas the air cooled bullet of higher alloy will remain a lot more consistent in its flow behavior. Up to a point the two alloys will act the same, but past a certain stress level the milder alloy's artificially-induced, strong lattice structure will crush and it work-softens back to its "base" BHN. The ability of the heat-treated alloy to work like a tougher alloy in the gun and a weaker one when it hits something can be a big advantage for hunting bullets if exploited carefully.

Sometimes one alloy is better than the other at the same hardness, it just depends on what you need the alloy to do for you. Discussing the "depends" part will make an interesting conversation.
 

Gary

SE Kansas
I cast for pistol mainly, and plinkers for rifle. I've never really been concerned with BHN since I don't load cast for hotrod runs.
 

CWLONGSHOT

Well-Known Member
Thats my next endeavor. Heat treating.

i was sorting cast last night and found a coffee can full of LEE400-145’s I cast about 18-19 months ago. Can was labeled 10/11 BHN. Now normally I dont trust my LBT BHN testor on PC cause the PC is soft and gives false or inaccurate readings. But the one bullet right on top had a very thin coating on its meplat. So I snatched it up to test.
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we all know that they harden with time with antimony, arsenic and Tin. But I was surprised as IIRC, these where like 20-25% hard and rest soft lead.

Whats a “regular” heat treat? Say 30min @ 400 or longer and will longer equate to harder?
 

fiver

Well-Known Member
1 hour to heat soak properly.

when I P/C it takes me an hour + to get everything up to the end of full 20 minute 400-410 cook temp in my oven.
there is also the hardness of the coating itself to take into consideration when your trying to take a reading.
I don't know what powder should harden to as far as a BHN.
I have heard up to 35 that's about the same hardness as lead oxide [and maybe tin itself] airc.
 

Dusty Bannister

Active Member
Quoted: i was sorting cast last night and found a coffee can full of LEE400-145’s I cast about 18-19 months ago. Can was labeled 10/11 BHN. Now normally I dont trust my LBT BHN testor on PC cause the PC is soft and gives false or inaccurate readings. But the one bullet right on top had a very thin coating on its meplat. So I snatched it up to test.


I believe you could be introducing that error in reading due to poor sample prep. The LBT instructions require a flat nose and flat base. That means sanding off the nub on the base if there is one. No reason to not sand that same plastic coating off both the base and nose to get a correctly prepared sample. You will probably get quite a different reading.
 

Bret4207

Undesirable member in absentia, Northern NY
I don't have the educational background to offer anything in the lines of "so and so % of this is better than % of that". What I can say is that I gave up worrying about Bhn and adding tin or antimony or arsenic or old lace or the toe nail clippings from a virgin unicorn long ago. I find mixing up BIG batches of alloy and working with what I've got serves me a lot better than mixing up dozens of small batches trying to find some magical mix that allows me to treat lead alloy like a jacketed bullet. No, I can't shoot my alloy at 2500fps without getting some leading, serious leading in some guns. But I don't NEED to shoot at 2500fps anyway, so whats the big deal? I can shoot, or could when I could see, at 21-2200fps out of a 308 or 35 Whelen and plop them in groups of about the same size as I got with jacketed at 100 yds. I'm good with that.
 

CWLONGSHOT

Well-Known Member
Quoted: i was sorting cast last night and found a coffee can full of LEE400-145’s I cast about 18-19 months ago. Can was labeled 10/11 BHN. Now normally I dont trust my LBT BHN testor on PC cause the PC is soft and gives false or inaccurate readings. But the one bullet right on top had a very thin coating on its meplat. So I snatched it up to test.


I believe you could be introducing that error in reading due to poor sample prep. The LBT instructions require a flat nose and flat base. That means sanding off the nub on the base if there is one. No reason to not sand that same plastic coating off both the base and nose to get a correctly prepared sample. You will probably get quite a different reading.
Under stood. I didnt type it but base was dead flat or I couldnt have tested.
CW