How does hardness affect accuracy?

[BCM45]

Like the title says how does the hardness of a boolit affect it's accuracy? Would a boolit with a BHN of 5 shoot worse than one with a hardness of 12 or 13?

[R.M.]

There is no real way to answer that. Every gun is unique, and what may be dismal in one gun, may be great in another.

[500MAG]

Hardness between bullet lots can effect velocity and subsequently accuracy.

[paul h]

It depends on the application, i.e. how well the bullet is sized to the bore, what the twist rate of the barrel is, what pressure the load generates, and some other factors as well.

In the case of a low pressure low velocity load, the softer bullet just may be more accurate. In the case of a high pressure high velocity load, the soft bullet will literally be torn apart by the rifling in the barrel and accuracy will suffer.

There are no absolutes in casting, you have to taylor the size, alloy, harness and size of the bullet for the application for best accuracy.

[gbrown]

Go down to the bottom of the page here and look at Cast Bullet Notes from LASC. Look at the Cast bullet alloys & alloy maintenance thread by Rick Kelter. Read it all, is all I can say. Also, the "Cast Bullet Articles of Glen E. Fryxell." These are the info topics you are looking for.

[btroj]

Paul h was pretty much dead on. It is all about having a balance between alloy, size, lube, pressure, powder speed, and many other things.

[Doc Highwall]

The most important thing to start out with is bullet fit. Even a light load will not shoot good if the bullet is too small. After bullet fit the hardness and lube come into play.

Shallow micro groove rifling like in the Marlin's make bullet fit and hardness more important the regular rifling, but that is not to say it is not important with regular rifling.

[BCM45]

Thanks for the help guys.

[Marlin Junky]

It also depends on the pressure function associated to the shot; i.e, softer boolits require slower powders. Nevertheless, for typical rifle loads you will be much better off with an alloy in the 12-13 range than pure lead. Usually, a "scrap" Pb alloy will be easier to find and less expensive than pure Pb. Pb alloys also respond to heat treating. Range scrap is good if you've got the time and opportunity to collect it.

MJ

[Char-Gar]

Like the title says how does the hardness of a boolit affect it's accuracy? Would a boolit with a BHN of 5 shoot worse than one with a hardness of 12 or 13?

There far to many factors and variables to give any kind of informed answer to your question. It would take a small book to covered the subject. There are such books out there, think about buying one.

[runfiverun]

this is a good opportunity to throw some revolver loads out there with some fast,medium,and slow powders.
along with the alloys that worked with those loads best. [accuracy wise]
a sampling of the loads would figure things out pretty quickly.

[popper]

alloy, size, lube, pressure, powder speed As a new caster I wonder about it also. We have the Lee formula, BHN vs FPS recommendations, spin-rate equation, etc., but not as a sticky. The gun, size, lube & CB design aren't really part of the BHN or fps equation. I assume most of us don't have a chrony, BHN or psi tester so we test by leading and accuracy - results. Maybe a poll by cal, alloy (BHN), gun style, fps (hot, med., light), powder speed # would allow a better consensus of what works well. Or maybe we just use whatever we have and put up with the results. Any thoughts? I see the same questions about lube and similar responses.

[subsonic]

If the fit and lube are right, harder is more accurate.

No cast boolits are as hard as jacketed.

Flame on!

[40Super]

Having every bullet in the same batch , the identical hardness as each other is more important than the actual hardness #.

[white eagle]

fit,fit and fit that what it all comes down to
when fit is king all the other things fall into place
bhn is a number for having a number.... place no great emphasis on it
and the velocity is useless if you do get an accurate load with it
worry more on the guns dimensions or as we relate to our gals their figure

[runfiverun]

forget the lee formula.
his max is usually a good place to start.
i do have a chrony and a bhn tester.
both are very good ones,but they cannot predict accuracy only tell me what's up with a load or a bhn number.
they can be used to fine tune a load that is close or help reject one that isn't.

assuming the gun has no mechanical issues.
if you balance the hardness with the boot the powder is giving it things will go along better.

[popper]

Not trying to predict accuracy, just want to avoid making it worse. If it didn't matter, we'd all be using pure Pb. Formulas only work when correctly applied.
Balance the hardness with the boot the powder Totally agree, but that takes a lot of trial and error & $$$. Lots of opinions here, collecting them may give a better guess at what is needed in the alloy. I can choose fit, powder, lube, fps and alloy. The OP's question (and mine) is a starting alloy to get good accuracy for the intended use.

[.22-10-45]

Hello, everyone..Interesting posts! Now here is a stumper.. For my 1-14" twist shillen barreled Hornet, I usually use a diluted alloy of Steriotype & pure lead..softer than Lino. I cast up some straight Steriotype bullets..Lyman 225415..the older 45 gr. style, and some custom Leeth 52 grainers. The Leeth bullets will shoot in 3/4" all day at 100yds. with the diluted Steriotype. Using straight ST, they were all over the shop..yet the little 45gr. 225415's
grouped in around 3/4" or so. Wonder why?

[paul h]

If the fit and lube are right, harder is more accurate.

No cast boolits are as hard as jacketed.

Flame on!

That has not been my experience with handgun bullets, and even with my limited experience with cast in rifles, I've found air cooled ww's to be as accurate as water quenched in my applications.

Now, if you have an application where a bullet is too soft for the given pressure of the load and twist rate of the barrel, then you simply have to have a harder bullet. But in the case of not pushing those factors to the limit, I haven't found a harder bullet to magincally tighten groups.

[mainiac]

Hello, everyone..Interesting posts! Now here is a stumper.. For my 1-14" twist shillen barreled Hornet, I usually use a diluted alloy of Steriotype & pure lead..softer than Lino. I cast up some straight Steriotype bullets..Lyman 225415..the older 45 gr. style, and some custom Leeth 52 grainers. The Leeth bullets will shoot in 3/4" all day at 100yds. with the diluted Steriotype. Using straight ST, they were all over the shop..yet the little 45gr. 225415's
grouped in around 3/4" or so. Wonder why?

Sounds like what i have found with my 16 twist hornet,it will shoot under an inch 50 yard groups with WDWW, and one time i cast up some 225415 with straight lino,and them boolits,at the same speed wouldnt shoot under 4-5 inches. Never did figure that one out..........They were pretty boolits,and casted very clean,was driving them to standard accuracy speed in my gun,about 2300 f.p.s.

[375RUGER]

If the fit and lube are right, harder is more accurate.

No cast boolits are as hard as jacketed.

Flame on!

Not flaming. The thought had crossed my mind. Yesterday,while i was checking the hardness of some boolits, I measured the hardness of a j-word, about 26-30bhn. I use a 60# weight over a single stage press to measure. Maybe somebody else has done a little more testing.

Difference in material properties and how each acts under pressure and speed, sounds like a lengthy discussion. :popcorn:

[John Boy]

The issue of the right hardness is based on the PSI of the reload ... multiply the alloy BHN by 1,422 = PSI

Use a hard alloy with low pressure = bullet won't obturate properly
Use a soft alloy with a high pressure = gas stripping and leading = poor accuracy

http://www.lasc.us/CastBulletNotes.htm
Approximate "Maximum" Chamber Pressure For Lead Alloys (PSI)
Plumbers lead, stick on WW 13,000 - (Black Powder Only)
Wheel weights / clip-on
25,000 - Non-Magnum handgun
loads, Rifles to 1,900 fps

Lyman # 2 (alloy varies in

Lyman cast bullet books)

35,000 - Magnum handgun &
rifles to 2,000 fps

Quench-cast WW (dropped

from mould into cool water)

48,000 - Magnum handgun
& rifles to 2,200 fps
Oven heat treated WW
55,000 - Jacketed velocities in handguns
and rifles with quality bore & balanced load

Bullet BHN / "Minimum" Chamber Pressure For Lead Alloys (PSI)
The formula (from the pages of HandLoader Magazine) to determine at what pressure an alloy of given BHN will obturate the base of the bullet and seal the bore. If the bullet is too hard to obturate, gas cutting usually occurs on the base band on the non-driving side of the rifling and barrel leading is likely. Simply multiply the alloy BHN by 1,422.
Example: Alloy BHN of 12 multiplied by 1422 = 17,064. An alloy of 12 BHN should be used with a load that develops a "minimum" of 17,000 psi. Need more info on minimum / maximum alloy BHN? These Glen E. Fryxell articles explain alloy BHN in easy to understand language.

[357shooter]

To the OP: For 357 magnum revolvers, I've gotten the best accuracy with soft oversized bullets. That's true for light loads as well as magnum loads. BHN 7-9 are the most accurate in any 357 revolver I've owned.

In my 357 lever action rifle the magnum loads shoot as much as 400 FPS faster and like BHN 10-11 the best. For non-magnum loads in the rifle, BHN 7-9 are the most accurate.

So depending upon what caliber, type of gun and load you use, the most accurate BHN may change a little.

In this case, softer bullets are in fact more accurate than harder bullets. Even WW alloy bullets are less accurate than softer bullets.

I figured this out by casting and testing alloys and loads, which is what you need to do to figure out what shoots the best in your gun and caliber.