BHN and Powder Selection

[mbruce]

So there I was reading the Lee reloading manual... and I'm not sure if I'm interpreting what I read correctly --

Here's what I have....

Missouri Bullet company 9mm 115gr RN BHN 18

So based on the max pressure calculations I need to select a load that will have a maximum 22,852psi .... when i look thru my load books there are none.

Missouri Bullet Company .45acp 185gr Button SWC BHN 12

Based on calcs.. need maximum 15,536psi.... according to Lee only unique, red dot, green dot, blue dot, herco, bullseye are in that range.

230 gr rn... unique, red dot, green dot...

So I must be interpreting this wrong because MBC isn't going to produce a 9mm bullet that is prone to leading because of a BN whose max psi is lower than the psi incurred on most 9mm loads...

I know this is only one aspect of leading ...and it depends on where it is in the barrel as to what the cause is....but just curious to know if im interpreting Lee's BHN max PSI correctly.

So too much pressure and too little of pressure can cause it...so it's basically just trial and error? -- or do you calculate the max PSI using the BHN (if known) and start from there? I've read in many other posts on here to increase the powder charge to prevent it....but doesn't that go against the MAX PSI calculation?

Thanks!

 

[fecmech]

Don't get too hung up on Mr. Lees calculations. The 9MM and lead can be problematic but BHN 18 will work if the size is ok and that is the problem with many 9's. Many have groove diameters .357 and .358 and .355 or .356 bullets will lead badly under those conditions. Before you buy any bullets for a 9MM I would recommend slugging the bore and getting a bullet at least .001 over groove diameter.
As far as .45's they are very lead friendly and bores are very uniform and the normal .452 lead bullets are generally trouble free.
Ask Mr. Lee how it is that .22 rimfires which are almost pure lead function so well at 1200 fps and 25,000 PSI.

 

[Walkalong]

Based on calcs.. need maximum 15,536psi..........................................................
So I must be interpreting this wrong because MBC isn't going to produce a 9mm bullet that is prone to leading because of a BN whose max psi is lower than the psi incurred on most 9mm loads...

Max pressure for 9MM is around double that. (More IIRC - 35K?) Anyway, 18 BHN is fine for 9MM unless you are running really light loads. Even then if bullet fit is good enough you'll probably be OK.

 

[mbruce]

I would recommend slugging the bore .

I was just reading on slugging a bore.... From the looks I just need a lead fishing weight, a dowel rod, and a mallet...oh and the grease... is that what you'd recommend?

 

[243winxb]

9mm & Lead & Lee

So based on the max pressure calculations I need to select a load that will have a (needs to be below maximum) maximum 22,852psi .... when i look thru my load books there are none.

Correct, no load for that bullet at BHN18.

just curious to know if im interpreting Lee's BHN max PSI correctly.

Yes, you are correct. Use Bullseye, with a target loading.

...so it's basically just trial and error?

Yes, been casting for many year, never tested for hardness, except with a thumb nail, but always added some linotype for the hot loaded 44mag/357mag.

 

[USSR]

mbruce,

Don't get yourself all wrapped up around the BHN/PSI correlation. Proper bullet sizing and lubing is perhaps 90% of what you need to concern yourself with.

Don

 

[fecmech]

I was just reading on slugging a bore.... From the looks I just need a lead fishing weight, a dowel rod, and a mallet...oh and the grease... is that what you'd recommend?

That's about right but don't use a wooden dowel, they can mushroom and really get jammed up in a barrel. Get some brass, aluminum or even steel 1/4" rod at Home Depot. If you're careful you won't hurt the barrel. Clean your barrel and lightly oil it and the lead slug, then pound it through. Measure with a micrometer and go from there.

 

[onebigelf]

Walkalong- good memory. Standard pressure 9mm is 35,000psi. +P is 38,500psi.

Regarding using the 1/4 rod to slug the barrel, if you wrap the rod in a strip of paper it'll keep the rod centered and off your rifling. Not enough paper to be tight, just to keep it centered.

 

[Jeff H]

mbruce,

Don't get yourself all wrapped up around the BHN/PSI correlation. Proper bullet sizing and lubing is perhaps 90% of what you need to concern yourself with.

+1 Bullet size is probably the single most important.

 

[LiveLife]

+1 Bullet size is probably the single most important.

Ideally, you want to be 0.001" over for tight seal with the barrel, but I load for several different pistols with varying barrel groove diameters. So for higher pressure 9mm loads, I focus more on the bumping of the bullet base (obturation) to get a tight seal and minimize gas cutting and leading. For lower pressure 45ACP loads, I focus more on the bullet diameter vs barrel groove diameter fit.

So based on the max pressure calculations I need to select a load that will have a maximum 22,852psi .... when i look thru my load books there are none.

No, the formula calculations will give you the minimum cartridge pressures that will deform the bullet at specified hardness.

Pressures needed to "obturate" the bullet properly = BHN x 1,422 x 0.90:
12 BHN = 15,357 CUP
18 BHN = 23,036 CUP
21 BHN = 26,875 CUP
24 BHN = 30,715 CUP

So for 18 BHN bullets, you'll need load data that produces 23,036 CUP or higher to obturate the bullet. (see sample 115/125 gr 9mm CUP chart below) I used to shoot 24 BHN bullets made by a local caster, but I needed to push them at high to near max load data to minimize gas cutting/leading. With 18 BHN bullets, I can use start to mid range load data and still get good obturation.

115 gr LRN W231/HP38 - Start 4.3 gr 28,400 CUP- Max 4.8 gr 32,000 CUP
115 gr LRN Titegroup - Start 3.9 gr 25,800 CUP- Max 4.3 gr 30,500 CUP
115 gr LRN Universal - Start 4.0 gr 24,400 CUP - Max 4.5 gr 31,300 CUP
115 gr LRN HS-6 - Start 6.4 27,900 CUP - Max 6.9 gr 32,200 CUP

125 gr LCN W231/HP38 - Start 3.9 gr 25,700 CUP - Max 4.4 31,200 CUP
125 gr LCN Titegroup - Start 3.6 gr 22,900 CUP - Max 4.0 gr 30,400 CUP
125 gr LCN Universal - Start 3.8 gr 24,400 CUP- Max 4.3 gr 31,300 CUP
125 gr LCN HS-6 - Start 5.9 gr 24,400 CUP - Max 6.6 gr 30,700 CUP

And for 12 BHN bullets, you'll need load data that produces 15,357 CUP or higher to obturate the bullet:

200 gr LSWC W231/HP38 - Start 4.4 gr 11,000 CUP - Max 5.6 gr 16,900 CUP
230 gr LRN W231/HP38 - Start 4.3 gr 12,200 CUP - Max 5.3 gr 16,900 CUP

So you may ask, if you use 18 BHN 45 ACP bullet, you'll need to generate 23,036 CUP or higher to properly obturate the bullet? Yes, according to the formula. I use 5.0 gr of W231/HP38 for 18 BHN 200/230 gr 45ACP bullet sized at .452", but my M&P45 barrel's groove diameter is .451", which provides a tight bullet to barrel fit. I get very little leading at chamber end and no leading down the barrel.


BTW, CUP and PSI are not the same and not interchangeable.

Here is SAAMI centerfire pistol spec PDF (pages 11 and 15) that has comprehensive cartridge pressures and specifications:

9mm 115 JHP - 33,000 Maximum Average CUP (Copper Units of Pressure)
9mm 115 JHP - 35,000 Maximum Average PSI (Pounds per Square Inch)

Here's an article that compares cast bullet alloys and obturation:

Using the RCBS 45-255 Keith SWC mould, I cast one batch of bullets with wheel-weight alloy (plus about 1% tin), and a second batch using linotype alloy. The wheel-weight bullets weighed an average of 266 grains, while those cast of linotype weighed an average of 255 grains. All bullets were sized .452" and lubed with my homemade moly lube (equal parts beeswax and Sta-Lube Extreme Pressure Moly-Graph Multi-Purpose Grease), loaded over 9.0 grains of Universal Clays into W-W cases, and primed with Federal 150 primers. These .45 Colt loads were then test fired for velocity (all chronographing was done within a 1 hour period, under constant weather conditions). The results are summarized below:

Velocity Data From .45 Colt Trials with RCBS 45-255 Keith SWC

Bullet/Gun - 3" S&W M625 - 4 5/8" Ruger Black Hawk - 6" S&W M25 - 7 1/2" Ruger Black Hawk
Linotype (255 gr) - - 838 fps - - - 887 fps - - - 872 fps - - - 940 fps
WW (266 gr) - - - - - 879 fps - - - 942 fps - - - 947 fps - - - 999 fps
Difference - - - - - - -41 fps - - - - 55 fps - - - - 75 fps - - - - 59 fps

No, the numbers are not transposed. The lighter, harder bullet was traveling an average of 58 fps slower than the heavier, softer bullet in what was otherwise identical ammunition ... All else being equal, the lighter bullet should end up going faster, and the fact that it was found to be slower indicates that some of the energy was lost as a result of gas leakage around the linotype bullets. This is due to the fact that this .45 Colt load generates only moderate pressure (about 16,000-18,000 psi) and the linotype bullets (BHN 22) were too hard to "bump up" and seal the bore effectively, whereas the softer wheel-weight bullets were able to do so (wheel-weights have been variously reported to have a BHN between 9 and 12, I generally use 10 as being representative). Using the empirical correlation outlined above, the linotype bullets would require a peak pressure of almost 32,000 psi to seal the bore effectively, while the wheel-weight bullets accomplish this feat at a modest 14,000 psi (easily surpassed by this load).

Another article on cast bullet alloys and hardness application:

Once the bullet is engraved, if the land/groove width varies, then the seal is broken on the trailing edge. How many times have you seen barrel leading "follow the rifling"? That is a sure sign that the bullet was too hard for the pressures generated by the load. This is why bullets of moderate hardness are desirable, by obturating they can seal this trailing edge. At extremely low pressures (e.g. 600-700 fps) obturation isn't quite as important since at these low pressures blow-by isn't as much of a problem and the lube serves as a floating fluid gasket and seals the gases (thereby limiting blow-by). Unfortunately, at the higher pressures that most sixgunners operate at, the lube gets blown out the muzzle if it doesn't have obturation playing a supporting role.

So, for routine sixgunning applications what do we want from our cast bullet alloy? In the 800-1000 fps range we should probably keep the alloy at a BHN of 12 or below. From 1000-1400 fps, 12 to 16 is a very useful range of hardness. For velocities of 1400 to 1700 fps, this window slides up to 14 to 20. Above 1700, linotype at a BHN of 22 is an excellent choice.

 

[zxcvbob]

Missouri Bullet company 9mm 115gr RN BHN 18

So based on the max pressure calculations I need to select a load that will have a maximum 22,852psi .... when i look thru my load books there are none.

You're overthinking it. You want at least 22852 if the bullets are a little undersized. If they are a little oversized, it doesn't really matter.

Just try them first. If you have problems, then you can try to figure out why. I shoot plain based cast bullets in my BHP, loaded to about 38000 psi, and they don't lead. I wouldn't blame them if they did, but they don't.

 

[243winxb]

i give up, i am going to cast some bullet, this is a waste of my time.

bds said >

So for 18 BHN bullets, you'll need load data that produces 23,036 CUP or higher to obturate the bullet.

For a BHN 18, Lee's chart has a PSI, then a safe maximum of 22,852 PSI. AS i understand it, your not to exceed/go above the 22,852psi. Someone has it wrong.

 

[LiveLife]

SAAMI maximum average pressure for 9mm (pages 11 and 15 of PDF).

33,000 CUP
35,000 PSI

 

[mbruce]

I focus more on the bumping of the bullet base (obturation) to get a tight seal and minimize gas cutting and leading. For lower pressure 45ACP loads, I focus more on the bullet diameter vs barrel groove diameter fit.

"Bumping of the bullet base" means changing the shape of the bullet..or making a smaller bullet a larger bullet? I googled and looked in past posts and really didn't get any good info on what "bumping of the bullet base" entails.

Thanks!

 

[Walkalong]

Pressure "swages" the bullet to fit the barrel/cylinder throats etc. The pressure on the base makes it expand.

 

[Walkalong]

Oh yea, there is BHN, and then there is hardness. BHN is a good guide, but not the final say in bullet "hardness" and how much pressure it will take to make it obturate.

Two 12 BHN bullets can have different lead, tin, and antimony percentages.

 

[USSR]

Some good posts here. I will only say, Bullet casting is an art, not a science.

Don

 

[LiveLife]

Oh yea, there is BHN, and then there is hardness. BHN is a good guide, but not the final say in bullet "hardness" and how much pressure it will take to make it obturate.

Two 12 BHN bullets can have different lead, tin, and antimony percentages.

I know, I know. And let's not get into lead alloy strength and malleability.

I was just trying to help answer the OP's question on BHN calculations when he read Lee's max pressure chart and could not find a load in the load books. BTW, he's not the only one. The article Lee's website references for their Hardness Tester says this:

The only piece of information in the chart I might question is the "Max PSI" column. I am not sure if the reference is an issue of gas cutting, or bore leading. According to the chart, a very popular #2 alloy carries a 16 BHN, has a strength indictor of 22,703 PSI and should be limited to 20,000 PSI as maximum pressure. Wheel weight alloy with a BHN of 9 carries a strength of 12,748 PSI and a MAX pressure rating of 11,473 PSI. The terminology is a little vague. Is this peak, max average, sustained for some period of time? I assume, because there is no reference to terminal velocity, this is a material yield strength and based on calculation; single digit odd numbers at the end of a number expressed in multiple tens of thousands. I believe this portion of the information isn't particularly authoritative in determining limitations*.

(* While the slip sheet does not present the detail behind the "Max PSI" entries, the basis is well defined in detail in "Modern Reloading" 2nd edition Chapter 10, page 129. Many thanks to RPJ for bringing this to my attention. Comment Added 10-13-05)

 

[mbruce]

So the is the overall consensus to just forget about Mr. Lee and his BHN calculations and just shake the magic 8-ball then load up and trial and error it until you get it right? Or do people actually follow his ideas and factor loads based on the calculated max PSI?

bds put on a BHN/load clinic for us with post #10

 

[Walkalong]

Fortunately the bullet companies put out a great product for the most part. Try those 18 BHN bullets at two or three power levels. One or the other will work for you. It's not rocket science. Most times with a little experimentation you can get a great load easily. If 18 BHN 9MM bullets did not work, MBC wouldn't sell them, they would sell 15 BHN or whatever. Adjust your powder level up and down and you will find a great load. I would suggest picking out a mid level load for your chosen powder and work up. Something like W-231, HS-6, Unique, Universal, AA #5, WSF, N340, etc.

just shake the magic 8-ball then load up and trial and error it until you get it right?

Pretty much.

Bullet casters, (all of us amateurs included ), are the ones who need to worry about all that other mess.

Stop stressing and start loading.

 

[LiveLife]

Stop stressing and start loading.

+1 - It's about having fun reloading, shooting your reloads, having fun reloading again, etc.

I generally use powder manufacturer's load data for lead bullets. If I can't find lead load data for a particular powder/bullet combination, I reduce the available jacketed load data and do my load work up.

With MBC's 18 BHN bullets in 9mm, 40S&W and 45ACP, I find that using mid to high range lead load data usually results in loads that do not lead or minimally lead.

The minimal leading that I get is the black smearing near the chamber end that is the combination of burnt powder/lube fouling and some gas-cut "eroded" lead. Longer OAL that will reliably feed/chamber will reduce this leading. And God bless whoever came up with wrapping old bore brush with copper scrubber pieces (Chore Boy) idea. Now days, a few strokes of Hoppes #9 dipped copper wrapped brush will produce shiny clean barrels.

 

[mbruce]

Stop stressing and start loading.

HA...will do. better to prevent or attempt then to have a day at the range where you end up looking like a coal mine worker after a long day. Then you get home and get even more riled up because you have to clean a barrel that looks like hardened lava flowed down your bore.... i may have exagerated some...


Thanks to all for your replies.

 

[fecmech]

So the is the overall consensus to just forget about Mr. Lee and his BHN calculations and just shake the magic 8-ball then load up and trial and error it until you get it right?

YES

I started casting in 1970 when it was common knowledge and in every shooting rag that you could not shoot lead in magnum pistols because they leaded badly.
Fortunately I had a friend who told me that was BS, and I have been doing it ever since with plain old wheel wt metal. The load manuals in the 70's had some pretty stout loads that are no longer with us because with today's equipment shows they exceed current standards. In those days I always loaded max and wanted accuracy too so anything that wouldn't stay under 2" at 25 yds went down the road. I didn't even know about BHN until about 10 years ago.
As I said in a previous post slug the barrel and go .001 over groove and have at it. If your groove turns out to be.357" I notice Missouri bullet has some 125 gr "cowboy" RNs at .358 that would probably do just fine in the 9mm even at 12 BHN. Lets put it this way, if I had a .357 barrel and the choice was a BHN 18 bullet at .356 or a BHN 12 at .358 the .358 would be my choice. SIZE MATTERS!

 

[243winxb]

If you exceed Lees Maximum pressure you will get Plastic deformation

http://castboolits.gunloads.com/showthread.php?p=35425#post35425

This whole relationship centers around the elastic limit for the alloy you are using and what the elastic limit is. the elastic limit is the point at which stresses can occur to an object and it will return to it's relative shape. Once you have reached the deformation stage it no longer returns to relative shape. this is a very simplified version of this topic as it pertains to engineering mechanics of materials.

This is meant to be a guide and to keep you within safe/acceptable limits for pressure and alloy for your purposes. Obturated bullets do not mean that the shape has went through plastic deformation, just that it has expanded and stayed within the elastic limits of the alloy.

The formula does not take into account other factors that aide in reducing friction and thus combined forces on the cast slug. As stated above, one member is getting very good accuracy with soft (by most peoples standards) alloys in high velocity loads (for cast anyway).

Another factor not talked aobut is the pressure curve of the powder/cartridge combination. Does it spike quickly (fast pistol powder in rifle size case) or is it a gradual increase (full case of slower powder). Protection of the bullet base can also be a factor, we routinely do this by gas-checking, using lube wads, or fillers.

http://en.wikipedia.org/wiki/Plasticity_(physics) plasticity describes the deformation of a material undergoing non-reversible changes of shape in response to applied forces Obturate means to block or obstruct.

 

[Walkalong]

The bore will reshape the bullet if it expands over bore size such as in revolver throats.

Same with autos. Any expansion in the throat over groove diameter will be swaged back down.

The only problem I see with too much pressure is getting more velocity than the alloy's strength can handle and skidding past the rifling causing gas cutting.

I just don't see it as much to worry about.