Educate me about hardness...

[Ken73]

I've been doing my homework, trying to learn as much as possible; been on the LASC page about hardness (I did pick up a Lee Hardness Tester kit) but I don't quite understand why/when you'd need a harder alloy?

The LASC page shows where deformation takes place at or above PSI = 1440xBHN, but doesn't place an upper limit on it. Seems to me there would be one, otherwise we'd all be casting in pure lead?

I was under the impression that speed (fps) determined the hardness, and whether or not you needed a gas check.

Sorry for such a n00b question but I've been reading for hours and can't find a definitive answer. Anyone care to point me in the right direction?

:confused:

[btroj]

I don't just look at speed, I look at pressure. Think of two loads, same velocity. One uses a smaller charge of fast burning powder, the other uses a larger charge of slower burning powder. The aster burning powder develops much more pressure, that can cause gas leakage and require a gas check where the slower powder may not.

I don't know that an "upper limit" on hardness exists. I do know that hard allows require more expensive metals to make. Hard bullets also are a bad choice with low pressures in some revolvers. A bullet that can obturate to seal the bore isn't going to,lead in most revolvers, cast them too hard and they don't seal until pressure gets much higher. Light load, hard bullet can be a good leading machine. Fit also plays a role here, evens not undersized bullets are the worst if hard.

Hardness also matters for hunting. A really hard bullet may be brittle and shatter on big bones. Hard alloy also doesn't expand on impact very well.

It also matters how you got to that particular hardness. I can shoot a high Sb alloy and get hard bullets of I can shoot a lower Sb alloy and water drop. Both have same "hardness" but one is far more malleable and in my opinion a better choice for most of my shooting. I prefer to look at approximate alloy composition than hardness. Harness can be manipulated, composition tells the whole story.

In the end, hardness is ONE factor in cast bullet shooting. It is important but no more so than lune, pressure, velocity, and ,or most of all, fit. The "harder is better" thing just didn't work for me. I shoot way softer than i used to and get better results.m maybe it is because I pay attention to alloy composition and adjust it to match the desired results and application.

[largom]

As btroj said, hardness is only ONE factor in cast boolits. What kind of gun are you loading for? What is the purpose of the load, plinking, target, hunting? What is the twist rate of your barrel? Boolit design can also play a part as well as lube.

There is no definite answer for your question that will cover all applications. Thats what makes cast boolits fun and challenging.

Larry

[Ken73]

Thanks guys, this is the kind of input I'm looking for - not looking for a specific application (I have way too many to list) but instead to understand the "why" per say so I can understand what hardness I should make a boolit. What factors do I need to consider, and why? Are there calculations you use, or is it just guesswork?

[popper]

Definitely the required hardness (strength) is pressure related, the muzzle velocity is a function of pressure. That equation hasn't worked for me in pistol, I think it is close in rifle. For me, it is knowledge gained from this forum and experimentation. Think of a hammer and a knife - soft vs harder CBs. Softer to keep the bore sealed and harder to avoid stripping in the rifling. Another consideration is sizing and brass prep. I can shoot pure lead from my 40 auto with decent results, but it's a PITA to load. Harder gives slight improvement in accuracy and makes a BIG difference in loading. Hard costs a little more but loading is simpler. I chose harder. Same for rifle, which usually requires hard due to fps. I add Arsenic or sulfur to my alloy because I think it makes a tougher CB and allows better HT when needed.

[btroj]

I don't use any calculations. I don't measure pressure and I don't have a hardness tester.

My bullets are soft, hard, or in between. I am that non-scientific about it. I don care what the Bhn is, I only are if they work!

For targets you can shoot hard or soft. For hunting it is more critical to get an alloy that does what you want. Hard alloys and HP bullets don't always get along well.

Like was mentioned a lot of this comes with experience. I have a general idea what I want the bullet to do and I adjust the alloy accordingly. Might add more pure lead, might be more monotype.

Don't get too hung up on all these numbers. The gun and target will tell you what works and what doesn't.

Like I always say- ou learn more at the casting, loading, and hooting bench than you learn anywhere else. To cast some bullets, load em, and shoot em. Best way to learn.

Don't ever be afraid to try what "can't" work, itis amazing how often it does!

[**oneshot**]

BHN has it's place but I have learned from many others on this forum that Boolit Fit is more important than a specific BHN. If the boolit fits then you can use a wider range of BHN allowing you to tweek your alloy for what you need the boolit to do.

[Hickory]

Most shooting/casting (95%) can be done with BHN at between 9-12.
There are two way to harden lead;
1) Adding tin to lead will increase the hardness, but only a little, (up to 9-10 BHN).
This type of boolit material is very ductile and expands very well.
2) Adding tin and antimony to lead will harden it more than tin alone. Antimony is the real hardening agent.
The more antimony that is added the harder it gets, 24 BHN and more, to the point of becoming brittle, that will shatter on contact with flesh at high speeds.

Wheel weights has been the best source for lead until recently. WW have a have a good amount of hardness, about BHN 9.
But WW can lack the tin needed for a good fill-out of the boolit when poured in the mould. A 1% addition of tin will give you alloy good enough for velocity up to 1800-2000 fps with the right lube.

[Larry Gibson]

Ken 73

I was under the impression that speed (fps) determined the hardness, and whether or not you needed a gas check.

That is good for a general guide only. As mentioned there are many variables that can affect the top end for a particular alloy.

As far as cast bullets go, BHN is only 1/2 the equation. Malleability of the alloy (sometimes called "toughness") is the other half.

Larry Gibson

[sqlbullet]

As Larry says, speed is a guide, because it will infer pressure. All else equal, the faster load experienced more pressure.

And, BHN is at best half the equation.

And pressure is not just what is applied to the base of the bullet. That pressure may be well below the plastic limit of the alloy hardness you have. But what about the pressure caused by the mass of the bullet resisting the rifling.

The end result, as btroj mentions, is we are not equipped to measure all the variables at play, and are left with an empirical process of seeing what works.

[popper]

Nice thing about casting, cast a bunch, if not what you want, melt, change the alloy and try again.

[Bjornb]

You mention the LASC pages. Download the e-book "From Ingot to Target" by Glen Fryxell. I read parts of that book almost every day and there's always something new to me. Glen is excellent at explaining how the various alloys behave at various speeds, and it will help you get a better understanding of the entire casting process.

[canyon-ghost]

Also consider that an ingot of Linotype to harden lead only needs to be 2-6% of the total lead alloy, it's a very small amount. So, it is possible to alloy up your hardness.

With wheelweight, a guy can drop them straight from the mold into a bucket of cold water (caution: this is dangerous) and make water quenched bullets that are very, very hard.

A hardeness of 12 bhn is ten times harder than a hardness of 11 bhn. Each numerical increase represents 10 times the original. It's deceptively fast at hardening.

Good Luck,
Ron

[popper]

Ken73 - There is no upper limit. When you push the base of a CB, nothing happens until you get to the yield force. Then the CB shrinks in length and grow in diameter. If not constrained by the bbl, it would squish flat - think terminal expansion. Different alloys have different yield strengths, thus the formula is a guide to the PSI needed to exceed yield and cause bump-up (SAAMI term). The rpm formula relates the rotational force to the yield force, exceeding rotational yield force will cause deforming of the CB during flight. Worst case is an exploding CB. So the normal approach is to have a chamber PSI to cause bump-up, not allow rifling stripping and a fps/twist to not exceed the RPM limit that destroys the CB.

[357shooter]

It's a very general question. If you list what are casting for, you can idea of what BHN others use successfully for similar guns/caliber. For instance, 45acp shoots great with soft bullets, it doesn't need WW hardness.

For target shooting handguns, a lot of guys mix 2/1 or 1/1 pure to WW. Some cast softer than that and have great success.

If you are talking high velocity 30-06 bullets (outside of my experience and knowledge) the guys here can help with that too.

[Ken73]

Here's a list of what I currently shoot:

380 Auto
9mm Luger
44 LC
45 ACP

17 Rem
221 FB
223 Rem
6x45 (6mm-223)
6mm PPC
243 Win
280 Rem
7mm-08
300 BLK
30-30 Win
308 Win
35 Whelen
50 BMG

Most of the rifle calibers I'd like to shoot higher velocities (unless someone has a reason not to?) A few of them I'd like to run subsonic like the 300 BLK (which I'm already doing successfully.) The 50 BMG I'd like to run both super and sub with; I'm not quite as concerned about sub obviously because it's simpler to deal with (much slower) but the supersonic ones are the ones I'm concerned about mostly.

Handguns, not so much - I figured out it is ideal for them to be relatively soft and I'm not as concerned about them.

I have quite a bit of WW ingots, and some Linotype as well (maybe 2:1 ratio at the moment.) I'm debating on getting some foundry type as well (really hard) but not a lot. Also working on sourcing WW's as I've had to buy what I have now and not too thrilled about it. Would like to get some WW's from a local shop as cheap as possible and smelt myself (have a smelting setup already.)

[357shooter]

Wow, that's a lot of calibers, are you going to cast for them all?

Since you are good w/the handguns and shooting soft alloy I can't offer much help. The 9mm can be finicky, the other shoot well with WW mixed w/pure. So soft means BHN 8-10.

Lyman #2 is a great alloy and may work well for the loads that need something harder than WW. You can shoot plain base lead to high velocities, but gas checks make a lot of things easier when exceeding 1,600 FPS. I think WW would be fine in most or all of the calibers with a gas check, but I don't have any of those rifle calibers so what do I know.

However, the rifle experts will chime in.

Oh, Rotometals has an alloy called Superhard. It's an excellent way to easily add antimony to your alloy, at normal casting pot temps. It's worth a look.

[John Boy]

Ken, would you believe I use 1:10 alloy in a 220 Swift with a velocity of 2930 fps with a gas check that produces excellent accuracy at 300yds?

Lyman tests and furnishes the best accuracy in their manuals for all their bullet reloads using Lyman #2 which has a Bhn of 1:15 for smokeless powder reloads

As a general rule of thumb for rifle bullets, I use:
1:16 for long nose bullets
1:20 for short nose bullets

Current hard cast bullet manufacturers for all smokeless bullets use an antimony:lead:tin and arsenic alloy that ranges between Bhn 18 to 20

What I'm really saying is ... your firearm will tell you what alloy it likes for accuracy that has excellent obturation in the grooves and no gas stripping. Use the Psi = 1440xBhn formula for starters