Bhn ?

[Digital Dan]

It occurs there are different alloy mixes that will present the same BHN, example being simple lead/tin mixes and lead/COWW mixes with emphasis on lead with just a bit of COWW.

Question that arises, can one expect the same performance with say 30:1 (~9 BHN) and lead with just enough COWW to raise it to 9 BHN?

Anyone know?

[pjames32]

You can reach 9bhn with or without antimony. You need to decide if antimony is needed for hardness?

[Digital Dan]

Rephrase of the question: I have two alloy mixes, one with known constituents, the other is unknown. They have the same hardness, 10.4 BHN. Is it reasonable to expect the same performance even though I'm quite certain the alloys are different?

[OptimusPanda]

Rephrase of the question: I have two alloy mixes, one with known constituents, the other is unknown. They have the same hardness, 10.4 BHN. Is it reasonable to expect the same performance even though I'm quite certain the alloys are different?

Are they the same weight from the same mold?

[Oklahoma Rebel]

no, the one with more tin will deform without being as prone to fracturing as the one with antimony, even though they are technically the same hardness, they will behave differently. they will also weigh differently, though im not sure in this situation which one would be lighter/heavier. does that answer your question? have a good day, don't be afraid to ask any more questions-Travis

[Digital Dan]

Was more concerned with the interior ballistics side of the equation than terminal or exterior. Should have clarified that

[Harry O]

They will act differently. The one with tin will cast easier, shoot to a higher velocity without leading, and expand better in game. However, it will cost more. The one with antimony won't do quite as well, but it is cheaper.

[Digital Dan]

Thank you sir!

D

[Larry Gibson]

Harry O is essentially correct. BHN is only one half the equation, the alloy malleability is the other half.

Larry Gibson

[Crusty Deary Ol'Coot]

Digital Dan,

Some good answers here but ---------------

Then the question comes, what are you shooting it in and what is the end goal?

Crusty Deary Ol'Coot

[Digital Dan]

Ol' Coot, actually the question isn't so much what I'm shooting the alloy in so much as what I will shoot it in. Having mentioned previously that I've mixed a number of alloys for various purposes in the past which I refer to as Lyman #2, Dan's 1.75, 1.5 and 1.25. It occurred that I inherited some lead from a fellow and found one to have the same BHN as my 1.5 alloy, or 10.4. Haven't a clue what the constituency is, but will load it and see what happens.

Now I play eenie-meenie-miney-mo... .25-20, .30-30, .44, .38-55 and well that takes care of the squill guns....

[runfiverun]

the total make up of the alloy will determine how it reacts to being shoved forward under pressure.
9 bhn can be arrived at by at least 5 different alloy make up's, but so can the peak pressure your going to attain.
each alloy and pressure rise speed/sustainability time will react differently.
antimony isn't the bad guy and tin ain't always the good guy, and a mix of the two changes things considerably versus each one alone being used.

[Digital Dan]

runfiverun, in very general terms I understood that part about the pressures, just wasn't clear about how the alloy would react. Might be an indicator that I had half a wit and thought to ask the question, maybe...there's a quirk or three in the landscape that gave a hint that 9 ain't always 9, and 1+1 adding up to 2 might be true, or not....

As example, quite some time back a fellow I respect in the shooting world suggested I get over the hardcast theory and that was excellent advice. More recently I discovered that a fairly soft alloy successful at moderate velocity was prone to leading at low velocity. Didn't obturate I guess, if only because softer alloy worked fine with the same charge and velocity. Wish I'd learned this when I was 10.

On a lighter note, if you work on that prose a little you could make a caster's rap song (?) out of that. Made me smile.

This is what happens when you start with PB, Sn, COWW and Linotype in inventory then some well meaning soul gifts you a pile of mystery metal.

[mehavey]

BHN is -- by definition -- the force (lbs) per square inch at which a material will deform.
Nothing more. Nothing less.

For those families/alloys of metals commonly used for bullets: equal weight bullets of equal hardness/design will perform similarly when shoved down the rifled barrel under equal pressures.

[Larry Gibson]

"For those families/alloys of metals commonly used for bullets: equal weight bullets of equal hardness/design will perform similarly when shoved down the rifled barrel under equal pressures."

Probably a good rule of thumb for cast bullet use under 2000 fps. However, above that there can be a difference in performance (accuracy) under the same load and pressures. Case in point; AC'd linotype alloy bullets have the same BHN as WQ'd Lyman #2 alloyed cast bullets....21 - 23 BHN +/- yet, at HV, there is a distinct difference in performance when cast of the same design and pushed at the same pressures. There are other examples.

Larry Gibson

[mehavey]

Can't argue that things may go a bit non-linear past Mach-2.
i'll dig into it a bit more (I'll admit 2,200 is my max w/ #2/ALOX
at 15, but then I stay moderately Holiday Inn Express simple)

[mehavey]

it suddenly struck me that water-quenched alloys are structurally different than normal/air-cooled bodies, which have uniform hardness throughout. The WC'd bodies have relatively thin superhard crystaline shells on the surface -- think case-hardened -- while the interiors are soft.

I would indeed expect such bodies -- uniform vs thin-shelled -- to behave differently under extreme (especially rotational) stress.

[blackthorn]

it suddenly struck me that water-quenched alloys are structurally different than normal/air-cooled bodies, which have uniform hardness throughout. The WC'd bodies have relatively thin superhard crystaline shells on the surface -- think case-hardened -- while the interiors are soft.

I would indeed expect such bodies -- uniform vs thin-shelled -- to behave differently under extreme (especially rotational) stress.

Could you please expand on the above? I would like to know how (based on what) you arrived at that conclusion.

[mehavey]

Before we get to the rotational differences between uniformly-hard bodies, and bodies having non-linear hardness, could someone point actual measurements of quenched Lyman#2 please ? (Rotometals, so true #2)

I just poured two 530gr postells, and dropped them directly into ice water.

Cut in half, and measured over three depressions each, the interior mid surface measured 14.9
The exterior measured (gasp) 15.

[Larry Gibson]

mehavey

What you discovered through actual testing is the common alloys used in bullet casting when WQ'd or HT'd do not "case harden".....they actually harden all the way through. Lyman #2 WQ's to 21-23 BHN. Like many things we do there are variables so giving a 22.7 BHN, for example, would be somewhat incorrect.

Larry Gibson