BHN per caliber

[BJung]

What is the ideal BHN of cast bullets per caliber. Before casting, I found a BHN formula: BHN=Chamber Pressure/1440. By taking posted handgun chamber pressures, I was coming out with 14.6bhn for 45acp (21k/1440), 23bhn for 9mm (33k/1440), and 24bhn for 357/40cal (35k/1440). I used pencils to test ingots. Until recently, I merely cast the hardest ingots to 40cal, midrange bhn ingots to 9mm, and the softest for 38 and 45acp. Now I am beginning to rethink my needs. A recent search said 7-10bhn is best for 38 special, 11-15bhn is best for the 9mm/.357, 14-16 bhn is ideal for the 40 cal., and 7-10 bhn is ideal for the .45acp. Some casters are posting that hardness doesn't matter. But I think that the higher pressure calibers should have a harder alloy. Also, from another post of mines, some casters claim that bhn doesn't matter. Does bhn per caliber matter or not from your experience?

[OFFSHORE]

I've only been casting boolits for about 10 years now and learn something new all the time from this forum and my own trial and error. A basic rule of thumb that has worked well for me is 1 BHN per 100 FPS of muzzle velocity. From there you can go higher or lower depending what your barrel tells you it prefers. For most all my hunting ammo in handguns I run a 30:1 ratio 50/50 of COWW and pure soft lead with pewter (15lbs. COWW/15lbs. soft lead + 1lb. pewter) and this works great in my 357 MAX, 44 Mags, 45 LC and 454 Cas. - this is only about 12 BHN!!! Like I said, I'm purely a hunter, but I demand accuracy, so all my loads I tend to run hard or at magnum levels. Hope this helps you a little. You will get others with way more experience then me chiming in soon. Take care and good luck.

[Rickf1985]

Hardness is an elusive subject. you talk to 20 people you will get 20 different opinions, opinions being the key word. I think your numbers are a bit skewed, although I have never used the math approach in this case but all of your original numbers are way too high. I mean, 23-24 is fast rifle territory. Too hard will lead a barrel very fast since the bullet will not obturate to the barrel.

[Wheelguns 1961]

Here you gohttp://http://www.lasc.us/FryxellCommentsCBAlloys.htm

[Larry Gibson]

There is no "ideal" BHN for any caliber. The "ideal" BHN along with the malleability of the alloy will depend on the intended velocity, accuracy requirement and terminal affect desired for the bullet.

[dondiego]

I have been casting and shooting for over 50 years and have never known the BHN of any of my cast boolits.

[gunther]

Started out with wheel weights and have not seen a reason to change. They have gotten softer since 1970, and harder to find, but they still work. That includes 357, 38 special, 41 mag, 45 acp, 45 colt and 44 mag pistol ammunition. Admittedly, Only the 357 has seen very high velocity. In eastern Ky, 41's, 44's, and 45's don't need much more than warm 44 special energy levels.
The only problem I've had was with commercial, wheel weight, bevel base bullets in a 44. About 850 fps for a 250 grain bullet would lead like you wouldn't believe. It was accurate for 40 or 50 shots, but took an hour to get the lead out of the barrel. The Lewis lead remover got a workout.

[405grain]

BJung: The BHN numbers that your formula are giving you just don't add up. In example: 24 BHN for a 357 mag./40 cal? That would put your alloy between linotype and monotype. That's way too crazy hard. Almost all of your pistol calibers can be satisfied by alloys from 10 to 15 BHN depending on application. Rifle calibers can run from around 13 to 24 BHN depending on application, with 15 to 16 filling the bill for most shooting. If you use powder coating you can cast with softer alloys because the PC acts as a jacket.

Way back when, before there was an internet and lots of information was just passed word of mouth: when people were getting barrel leading from shooting cast bullets, the old timers would tell you that "you need a harder alloy". They're train of thought was that somehow the lead was getting rubbed off the bullet. They even thought that gas checks were for scraping the leading out of the bore. Today we know much better. Leading is caused by the hot high pressure gasses leaking past the bullet, vaporizing lead off the surface of the bullet. As the gases cool the lead vapor is condensed on the inside of the barrel. Once enough lead had built up inside the barrel it begins to gall and abrade more lead from the surface of each successive bullet.

As you can see, a bullet needs to be soft enough that it will obdurate and seal the bore. A tight gas seal is what prevents lead build up. Using progressively harder alloys simply prevents the bullet from being able to seal the bore, and actually makes leading worse. Now, cast bullets do need to have a mechanical strength that matches with the pressure and velocity that they're going to be shot at. Rifle bullets generally need to be harder than pistol bullets. But the "formula" for bullet hardness that you're working from sounds like "old school" knowledge that has long since been dis-proven. You would probably be better served if you were shooting much softer alloys.

[Rickf1985]

Here you gohttp://http://www.lasc.us/FryxellCommentsCBAlloys.htm

Wheelguns, your link is not working, at lest it isn't for me. I have a copy of it somewhere and I will post it if I find it.

Found it, right here on the site in the sticky's, Go to part 2 and 3 and then go on to "leading". The whole book is the best read you will ever have and the best education on casting ever printed.

http://www.lasc.us/Fryxell_Book_Contents.htm

[dtknowles]

"a bullet needs to be soft enough that it will obdurate (sic.) and seal the bore. A tight gas seal is what prevents lead build up. Using progressively harder alloys simply prevents the bullet from being able to seal the bore, and actually makes leading worse."

I don't believe this is completely correct. If you have the right size bullet it will seal the bore obturate (not obdurate) even if it is a very hard alloy.

First sins are using too small diameter bullets, tight throats in revolvers or bullets that get swaged down when seated in cases with tight necks.

Use too soft an alloy and the bullet will skid and not grab the rifling, this can create a path for hot gas to pass the bullet. This will hurt accuracy and cause leading.

Use to large a bullet and when the bullet is swaged down entering the rifling it will create fins on the base of the bullet that can melt being thin and if the don't melt off are going to hurt accuracy.

Gas checks prevent fins and help prevent skidding. Harder alloys and gas checks are only needed at higher pressures and velocities.

Soft alloys are fine for most applications if the bullet is the right size. Soft alloys can help if the bullet needs to bump up to be the right size because of other complications like chambers too tight for the proper size bullet.

Tim

[BJung]

I agree. When I first started casting, I recorded the formula to determine the correct bhn per caliber to identify which tested ingot would cast a better specific caliber. Then later, I did a quick search asking, "what is the ideal bhn per caliber". I didn't save the source. It claimed that the best bhn for 9mm was between 11-15bhn with 12bhn mentioned more than once. For 40cal, the best bhn was between 14-16bhn with 16bhn being the most mentioned. For 38 special and 45acp, the best was between 7-10bhn. I opted for the latter because as you said is getting next to lynotype. I think the a an accuracy load will vary based on the bhn. A future a test will prove this. I agree with you about obduration. I visualize pushing a cylinder of clay down a tube. From the pressure, the base would obdurate. A gas check will help control the pressure on the base to a point. Only then would a harder alloy allow a bullet shoot more accurately with more pressure.

[BJung]

I can't cite the source but I've read and recorded that a harder bullet should be sized .002" larger than groove diameter than .001"

[Digital Dan]

I usually try to be logical about things, but I HATE hard alloys. Paper patched pure lead is adequate for Godzilla.

And deer...
https://imgur.com/RENinxM