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I was doing some evening reading trying to find more information on bullet types and weight correlations and came upon another question which seems to confuse me. I was watching a video on leading and how bhn correlates to more or less leading but that in the past we used softer lead and were able to prevent leading by ensuring the bullets where obturating correctly. So I found a calculation correct if im wrong that is 1422 x bhn = minimum obturation pressure.

Does this mean that if the pressure in the cartridge does not meet this pressure the bullet will not properly seal the barrel?

Second question is if the bullet is properly obturaring is the bhn itself the determinate factor to how much velocity or pressure a bullet can take? Or is there other variable when ot comes to lead bullets?

Seem to be getting conflicting answers

Such as you need x bhn to be able to fire magnum loads and others say it has other variable.

Thanks in advance for all info
 

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I was doing some evening reading trying to find more information on bullet types and weight correlations and came upon another question which seems to confuse me. I was watching a video on leading and how bhn correlates to more or less leading but that in the past we used softer lead and were able to prevent leading by ensuring the bullets where obturating correctly. So I found a calculation correct if im wrong that is 1422 x bhn = minimum obturation pressure.

Does this mean that if the pressure in the cartridge does not meet this pressure the bullet will not properly seal the barrel?

Second question is if the bullet is properly obturaring is the bhn itself the determinate factor to how much velocity or pressure a bullet can take? Or is there other variable when ot comes to lead bullets?

Seem to be getting conflicting answers

Such as you need x bhn to be able to fire magnum loads and others say it has other variable.

Thanks in advance for all info

You'll find this in the technical section at Missouri Bullet Co.

"There is a formula for optimal bullet hardness which is simple and it is worth knowing:

Optimum BHN = PSI / (1422 x .90)
The PSI of your reloads is published in the reloading manuals. Take a typical .45 ACP load, using a 200-grain LSWC bullet — 5.0 grains of Bullseye. This load develops 900 FPS and is in common use among IPSC and IDPA gunners. The reloading manual shows that the pressure generated by this load is 20,000 PSI.

So, the formula for optimal bullet hardness is
20,000 / 1279.8 = 15.62


There it is! For this application — shooting a 200-grain LSWC at 900 FPS requires that you use a bullet with a BHN of 16 to 18 (round upwards a couple of BHN points for flexibility.)" ;)
 

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I was doing some evening reading trying to find more information on bullet types and weight correlations and came upon another question which seems to confuse me. I was watching a video on leading and how bhn correlates to more or less leading but that in the past we used softer lead and were able to prevent leading by ensuring the bullets where obturating correctly. So I found a calculation correct if im wrong that is 1422 x bhn = minimum obturation pressure.

Does this mean that if the pressure in the cartridge does not meet this pressure the bullet will not properly seal the barrel?

Second question is if the bullet is properly obturaring is the bhn itself the determinate factor to how much velocity or pressure a bullet can take? Or is there other variable when ot comes to lead bullets?

Seem to be getting conflicting answers

Such as you need x bhn to be able to fire magnum loads and others say it has other variable.

Thanks in advance for all info
In reality, I've never had any problems with cast bullets at 17 - 18 BHN which is very common. Magnum revolver or slower loads in .45 ACP. There are some gun related issues you'll want to read about if you have a Lyman Manual.;)
 
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While I agree with the formula, I often find that my reloads don't develop the pressure/fps as advertised. I put this down to the following; my barrel maybe a little larger or smaller than one used to formulate the recipe, and/or my barrel maybe shorter or longer than the test barrel, and of course we maybe using different lot numbers of; primers, powder, bullets or cases.

And I might have pushed the bullet in or left it out +/- .004".

I see many variables that could stack or magically zero out.

While math is a great thing, cutting a 4 foot board in half, will not result in 2, 2 foot boards. :confused:
 

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Discussion Starter · #5 ·
In reality, I've never had any problems with cast bullets at 17 - 18 BHN which is very common. Magnum revolver or slower loads in .45 ACP. There are some gun related issues you'll want to read about if you have a Lyman Manual.;)

Now in days of old when catridge developers for the magnum rounds such Elmer Keith they were using 12bhn and were pushing it to the limit and did not have issues with the bullets or leading. Does that mean that anything below the high magnum pressures would the 12bhn seal the chamber correctly and work or is there a risk of grenading something running softer cast bullets at the 20-30k psi mark. Just trying to understand how all this works for the future. Im sure the softer 12bhn cost saving is appealing to all new reloaders lol

Once my plated and cast bullets deplete im picking up some bhn18 coated from mbc and some hornady jhp bullets.
 

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Now in days of old when catridge developers for the magnum rounds such Elmer Keith they were using 12bhn and were pushing it to the limit and did not have issues with the bullets or leading. Does that mean that anything below the high magnum pressures would the 12bhn seal the chamber correctly and work or is there a risk of grenading something running softer cast bullets at the 20-30k psi mark. Just trying to understand how all this works for the future. Im sure the softer 12bhn cost saving is appealing to all new reloaders lol

Once my plated and cast bullets deplete im picking up some bhn18 coated from mbc and some hornady jhp bullets.
That's interesting. IIRC, Elmer cast his own bullets for his hot .44 Specials. Can't remember his alloy, though. The big thing with revolvers is slugging the bore for groove diameter and measuring cylinder throats to make sure that they're not undersized. Plenty of people have load Lyman's No 2 alloy (15 BHN) for magnum revolver loads without leading issues.

The softer a bullet is, the easier it will obturate. When the .357 Magnum was introduced, the first loads were spec'd around 1600 FPS with a 158. It didn't take many of those rounds before you were scrubbing lead from the bore. Haven't seen much testing with softer poly-coated like the 12 BHN product that MBC sells. Think that would be interesting. The question would be how fast they can be pushed before the poly-coating is stripped away and potential leading occurs. I hope to see, eventually, poly-coated hollow-points, and they'll need a softer alloy for good expansion.

Even with what MBC states, with the correct size 17 -18 BHN bullets, they have caused minimum leading in my loads. But when in doubt, there are companies like Oregon Trails/Laser Cast that make an even harder bullet at around 24 BHN. The problem there is that they are so hard that they can break when striking bone. Most of he heavyweight, cast, game bulletmakers do not make their bullets so hard and many have gas checks on them to help prevent leading. I never bought into the idea that cast bullets have to be used on game. And, particularly not today. Jacketed Soft-Points and bullets designed for silhouette shooting like the Sierras, have lead exposed at the nose and can deform. Some expansion is better than no expansion.

For lower velocity target loads like those used in Bullseye competition, even softer swaged bullets, mostly wadcutters, are the name of the game. Swaged SWC hollow-points have done very well in defense shootings and the FBI used a 158 gr. SWCHP +P in their 3" model 13 Smiths before the transition to auto loaders. They're still available as component bullets and some companies like Buffalo Bore make loaded ammo.;)
 

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Watching with interest. I did some BNH calculations for my loading tables. But some bullet manufacturers use PSI and some use CUP. The BHN calc using CUP seems to be a little off when compared to the same weight bullet that provided PSI amounts. Using CUP with 125grn rnfp (coated) came up with 8-9 BHN. But most bullets I have shopped for run around 12 BHN - So am interested in this conversation. I have finished loading 50 38's using the 125 grn coated rnfp with a stated BNH of 12 and using 3.9grn of HP-38. I plan on running them this weekend and will report back on any excessive leading.
 

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Watching with interest. I did some BNH calculations for my loading tables. But some bullet manufacturers use PSI and some use CUP. The BHN calc using CUP seems to be a little off when compared to the same weight bullet that provided PSI amounts. Using CUP with 125grn rnfp (coated) came up with 8-9 BHN. But most bullets I have shopped for run around 12 BHN - So am interested in this conversation. I have finished loading 50 38's using the 125 grn coated rnfp with a stated BNH of 12 and using 3.9grn of HP-38. I plan on running them this weekend and will report back on any excessive leading.
The reality here is that most of us load cast bullets that are harder than they need to be, like cast SWCs in .45 ACP around 800 FPS for me. While the MBC system is a good one, I don't think it's perfect, just a useful guide. There are some casters here on the forum and hopefully, they'll weigh in. I had a melanoma dug out of my back in 1997, so I've never got into casting my own. In fact, one of the things I like best about using poly-coated bullets is that it significantly reduces your exposure to lead.

For a Target load where the formula tells you an 8 - 9 BHN is req'd. You won't have any problem using a 12 BHN bullet. Are they optimum? That likely depends on their use. 8 - 9 BHN is actually about what swaged bullets run, and the Bullseye competitors often use bullets that are .002" larger than groove diameter. BUT, they know their cylinder throat dimensions, and that's not as easy to get. Calipers, since their I.D. measuring probes are offset, can't give you the precise measurement. An inside diameter mic can. But we know that the more specialized that precision measuring instruments become, the more expensive they get. You can bet, however, that for Bullseye competition, the guys shooting revolvers will have a means of getting those measurements.

Here's a scenario: your .357 Magnum revolver barrel's groove diameter is .357" but the cylinder throats measure .356". Particularly as you go softer in BHN, the more likely the cylinders are to swage the bullets down to that diameter, and if they go into the bore after being swaged to a smaller diameter, leading can occur. Now, .357 Magnum or .38 Sp. is just an example. Most of the problems I've seen have been with .45 Colt loads. The original diameter was .454", but when reloaders started using Jacketed bullets made for the .45 ACP at .451", accuracy was less than satisfactory and the bulletmakers began making .452" bullets for .45 Colt. Even today, some companies like Sierra make a compromise and their .45 bullets are sized .4515". Anyway, it's these kind of variations that have caused problems for the .45 Colt.

Upon necessity, I have used harder cast bullets than typical for slugging a bore. Takes more time and patience, but it can be done. The simpler way to get these dimensions is with oversized swaged lead bullets. Just make sure that they are larger in diameter than the nominal diameter for the caliber. Slug the bore and slug the cylinders. As an example: for the 9 x 19mm pistols, I'd use a .358" swaged bullet. Also be aware that with revolvers, the cylinder throats may not be identical and why some guys have their revolver cylinders throated. Unfortunately, with the dominance of auto-pistols these days, finding a good revolver smith can be harder.

I have yet to slug my 4.2" GP100, but I have already ran .358" poly-coated bullets at .38 Sp. velocity without issue. I would not get overly concerned with good quality revolvers unless you have reason to be, i.e. leading develops. Starting with lower velocity loads will help.;)
 
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This sounds like a good job for a computer program, or a spreadsheet, if you know how to set it up.
 
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This sounds like a good job for a computer program, or a spreadsheet, if you know how to set it up.
At least keep a log for handload info. Something I was guilty of not doing for longer than I should have. Been running mine now since 2013. A spreadsheet would make it easier to find the info you're looking for. Maybe do both if you're so inclined. I have to try to remember a particular period that I was developing a particular load.;)
 
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