Lead Projectiles and BHN

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WrongHanded

WrongHanded

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The subject of BHN is one I know little about. I understand that a bullet which is too soft for the the chamber pressure will cause leading. And also that a bullet which is too hard for the chamber pressure will fail to obturate and result in gas cutting around the bullet, and also lead the barrel.

I have used almost solely SNS Casting coated bullets which they claim have a BHN of 16-17. I don't believe I've ever had a leading issue from them, despite running these bullets in a range of <800fps - 1,300>fps (at an estimate), and with relatively low pressures of .45acp and .38 Spl, up to book max for .357mag and .44mag (with some .45-70 GV'T at mid levels). However, the Missouri Bullet Company has a formula for correct BHN:

BHN = PSI / (1422 x .90)

This formula obviously gives quite different results for each end of this pressure range.

So I'm wondering a few things:

Firstly, how important is BHN when considering pressure and velocity?

Secondly, will the coating negate some of the leading potential cased by the bullet being too hard or too soft for the chamber pressure?

Thirdly (more for curiosity than anything), how hard does a bullet really need to be for handgun hunting or backwoods protection? I know a lot of people prefer "hard cast" for these things, but how hard is hard?

I'm not terribly concerned about what I'm using (they seem to make holes in paper just fine, and don't mess up my barrels). But I am interested in learning more about the subject.
 
http://www.lasc.us/Fryxell_Book_Chapter_3_alloySelectionMetallurgy.htm

When you read this you'll find that historically "hard cast" bullets had a BHN of 12 and a "soft" bullet, aka pure lead, a BHN of 5.1

Elmer Keith used an alloy of 16-1 with a BHN of 11 when developing the .44 mag.

BHN of 16-17 is way too hard for almost any handgun application.

I cast my own of a 50/50 mix of pure and clip on wheel weights. That gives me a BHN of around 10. I shoot this lead in .38 spl, .357 mag, 9mm, 10mm, .44 mag, and .45 ACP.

If my bullet fit is good I have no leading problems. Velocity ranges from 650 fps to around 1350 fps.

I use either Hi-Tek or powder coat on the bullets.

The commercial casters use hard lead so the bullets don't get deformed during shipping and handling.
 
In my estimation, BHN for cast bullets is highly over rated. I have shot many cast bullets running around 10 BHN in my 44 Magnums with little leading (I shot them for mebbe 15 years before I got a hardness tester). I had access to an almost unlimited supply of clip on wheel weights so 99% of my casting was done with that (and sometimes some range lead thrown in).

The single most important aspect of shooting cast bullets is bullet to gun fit. You can run a swaged soft bullet to well over 1,000 fps with no leading if the bullet to gun fit is correct (BTDT; Hornady swaged 158 SWC in a 357 Magnum). I believe the term "hard cast" started as meaning a hard bullet, like Lyman #2 or harder, up to Linotype, but now means very little, just a cast bullet. Hard bullets from commercial casters came mostly from new cast shooters thinking "harder is better" and the commercial casters just gave them what they wanted. Bullet hardness, BHN, does have meaning and worth, but mostly for performance on target rather than leading...

I've only been casting bullets for 25 years so my observations are my own, but they work for me! :p
 
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I have used coated bullets in several calibers from various manufacturers and some I cast and coated myself. I only recall leading issues with one gun, my BHP 9mm. I have pushed a few fairly fast in 357, 41 and 44mag also 45-70.
 
I had this same problem when starting casting.

A very close read of Fryxell will explain that the formula you found at Mississippi Bullets site is actually a 'starting' number.

In other words, the pressure has to be AT LEAST that high to obdurate the projectile.

Lower pressure will result in leading, but the pressure ceiling is unspecified.

To pick numbers at random for an example; if a 10Bhn needs 14k pressure to obdurate, that doesn't mean it will be too soft to shoot at 26k pressure. Only trying in each individual barrel will give you max pressure for that Bhn in that barrel.

I routinely shoot 10-12 Bhn at 1250-1300 fps in a 44Mag Ruger Super Blackhawk.
 
Like others have said, fit is king. Hardness less so unless you are pushing the bleeding edge. I cast lower pressure stuff from either range lead or clip on wheel weights plus some tin (roughly 10 and 12 BHN respectively). Rifle loads I have been casting from clip on wheel weights plus tin, but since these are always gas checked it is sort of a moot point. Until you get to really fast speeds (2000+ FPS) I don't believe a real hard bullet matters all that much. Realistically, my high pressure hunting rifle loads need to flatten/expand at impact, so I don't want the bullet to be too hard and either poke a small hole or shatter (if they are brittle). So I think hardness gets you very little. Fit, OTOH, is of paramount importance in my experience.
 
Thanks everyone! Very educational. Perhaps one day I'll start casting my own. For right now, what I'm using works well for me, but I sincerely appreciate all the input.
 
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