Bullet hardness questions. MBC, please weigh in.


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0to60
June 11, 2011, 07:08 PM
First, read MBC's essay on BHN and how CUP is used to determine a BHN that won't result in leading:
http://www.missouribullet.com/technical.php

Ok, now my questions.

1) In their example, they cite a .45acp round consisting of a 200gr LSWC over 5 grains of Bullseye, 900 fps at 20k CUP. I'm looking at several sources of reloading data, and 5 grains of Bullseye will push a 200gr LWSC somewhere south of 900 fps, at CUPs of around 15k.

I'm not trying to be a stickler here, but they use their numbers to arrive at a BHN that they claim will cause no leading. But, it looks to me like their data is significantly off, and if I plug what I believe to be more accurate numbers into MBC's formula, I'm getting BHNs of 12 or so. This is a big difference, as their website implies you use their BHN 18 LSWC for 5gr Bullseye. By MBC's own reasoning, this load should be producing a fair amount of leading.

2) MBC offers a ".357 Action!" round that's a BHN 18 158gr SWC, for "magnum velocities". A "magnum velocity" for a 158gr bullet out of a .357 magnum should be around 1300 fps. So I'm looking at reloading data and I'm seeing that, on average, that load should produce around 40k CUP. If I plug THAT number into MBC's formula, I get a requisite BHN of a whopping 32. How is it possible that MBC's BHN 18 bullet can be pushed to those velocities without causing significant leading, as according to their own explanation? Indeed, in a different thread, MBC has said that that bullet has been pushed as far as 1450fps without leading.

Now, I've read a lotta threads around here where folks are talking about their pet loads and whether they cause leading, and there seem to be a lotta cases where one guy says a load causes no leading, and another guy stopped using that load because it caused too much leading. So is this all a "your mileage may vary" thing? If so, that's fine, but where does that leave MBC's handy formula? Indeed, why pay attention to BHN at all if everyone is getting different results?

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glockky
June 11, 2011, 07:31 PM
Man i see where you are coming from I had a lot of problems because of this. I was new to lead and bought the 18 BHN 185gr swc's for my 45 and they ended up being a bust. They were just too hard I had them at midrange jacketed data and the lead wasnt as bad but i was just afraid to push them any farther which is what they needed.

Galil5.56
June 11, 2011, 07:37 PM
I've read a lot about formulas for what makes for the ideal hardness vs pressure used (BTW, C.U.P.S is measured in C.U.P.S, not P.S.I.), yet I have had success like many others "breaking the rules"... In my experience, proper bullet fit to the barrel/throat, plus good/proper lube matched to the job pays the largest dividend, but of course hardness/alloy used must be taken into account. Even if say commercial "hardcast" leads your particular barrel despite proper sizing, an application of Lee Liquid ALOX will many times cure it.

Also have to factor in the barrel used... Some barrels simply lead more than others even when "optimal" variables are used, same goes for copper fouling. If only it were so easy to say use X, Y, and Z, and get A, B, and C.

bluetopper
June 11, 2011, 07:56 PM
Really.........your barrel will probably not lead at all at either hardness. Pressure and velocity data is merely a guide. Pick a hardness and try it. You'll see, it's not worth fretting over.

The problem of leading, from my experience, is waaay overblown.........especially on internet forums.

USSR
June 11, 2011, 07:58 PM
You're over-thinking the BHN thing. Much more barrel leading is caused by improperly sized and/or lubed bullets than by too hard or soft bullets. Just use a reasonable hardness and make sure they are sized properly for your particular gun.

Don

0to60
June 11, 2011, 08:12 PM
You're over-thinking the BHN thing. Much more barrel leading is caused by improperly sized and/or lubed bullets than by too hard or soft bullets. Just use a reasonable hardness and make sure they are sized properly for your particular gun.

Don
Define "reasonable hardness".

murf
June 11, 2011, 08:19 PM
with the weapons you are using, reasonable should be 12, 15, maybe 18bhn.

murf

bluetopper
June 11, 2011, 08:26 PM
For instamce, I use the same 38 cal. 148gr DEWC bullet in my 38 for powder puff target loads as I do loaded in 357 cases stuffed full of as much 2400 powder as I can get in to it with no leading in either loading.

USSR
June 11, 2011, 08:46 PM
Define "reasonable hardness".

Tell me the cartridge and load.

Don

0to60
June 11, 2011, 08:51 PM
Tell me the cartridge and load.

Don
Umm... the ones I mentoned in my original post.

243winxb
June 12, 2011, 09:07 AM
45acp test. To me, leading is when accuracy is lost. Some barrels will look bad, but still produce the same accurate groups. Photos of test i run using 200gr swc hard, heat treated cast bullets with 5.0gr 700X. Accuracy was the same from first group to last. Click photo for larger view. http://i338.photobucket.com/albums/n420/joe1944usa/th_40shots.jpg (http://s338.photobucket.com/albums/n420/joe1944usa/?action=view&current=40shots.jpg) http://i338.photobucket.com/albums/n420/joe1944usa/th_IMG_4480.jpg (http://s338.photobucket.com/albums/n420/joe1944usa/?action=view&current=IMG_4480.jpg) http://i338.photobucket.com/albums/n420/joe1944usa/th_IMG_4494.jpg (http://s338.photobucket.com/albums/n420/joe1944usa/?action=view&current=IMG_4494.jpg)

Overkilll0084
June 12, 2011, 09:36 AM
MBC has a formula? Never noticed. At the end of the day they are inexpensive cast bullets. Just shoot them & enjoy.
I run the .45 Softball w/ 4.6 of bullseye. I get a hint of lead in the 1911 and slightly more in the Witness. Neither could be considered bad. A little solvent and a little brushing and it comes out.
I run the .357 Action from mild to wild. I find that leading is minimal up to 14.0 gr of 2400. Above that it gets worse quickly. 14.0 is plenty warm. It's accurate as well. If I want more, I'll find some jacketed.

For entertainment, get a sample pack of the 180 Strikers (.357). Very accurate and they put a serious thump on bowling pins.

336A
June 12, 2011, 09:39 AM
I learned about bullet leading the hard way several years back with my .38 SPL and .41 mag. I didn't do my research and got caught up in the harder the bullet the better it must be:rolleyes: Uncle Elmers' bullets were a BHN of 15 (Lymans standard #2 alloy) and he got by fine when useing them for his stout .44 loads.

Today when I'm looking to purchase cast bullets I want a bullet that is no harder than 16 BHN. These will work fine in both the .38SPL and .41 mag. The very first bullets I used were 18 BHN and they leaded horribly at the forcing cones of my revolvers. The reason they leaded in the .41 was I useing them to replicate the old police loading with 8gr of Unique.

243winxb
June 12, 2011, 09:50 AM
44mag test. Using mag. shot as an alloy, containing 6% antimony. Oven heat treated/water cooled. These very hard bullets left the barrel looking much like the 45acp bbl. Accuracy was very good. Bullet fit, with good lube are most important. Very soft alloys, close to pure lead will let a bullet skid, resulting in poor accuracy. I find bullets in the back stop with blue & red lubes still in the grease grooves, not so with NRA type 50/50 lube. I have to wonder if commercial lubes are getting the job done. :confused: After 40 years of casting, testing is the only way to know what works. Air cooled alloys with some antimony & tin, using NRA type lube, still gets the job done. :) http://i338.photobucket.com/albums/n420/joe1944usa/th_IMG_3306B.jpg (http://s338.photobucket.com/albums/n420/joe1944usa/?action=view&current=IMG_3306B.jpg)

Walkalong
June 12, 2011, 09:56 AM
As Don posted, there is more to leading than velocity or pressure and BHN. The alloy mixture makes a difference as well. Many different alloys can have the same BHN.

Also as Don posted, bullet size in relationship to our guns throats and barrel are much more important. With a good fit, we can get away with an alloy/BHN that may not be optimal, but with a poor fit, the perfect alloy/BHN will lead.

Buy some 12 BHN bullets for your 200 Gr .45 ACP loads, buy some 18 BHN bullets for your full strength .357 loads, and quit worrying about it.

Check the throats in your revolver to make sure they are not undersized. If they are, you must have them reamed to .001 over the bore (groove actually) size. I would rather have throats I need to ream than big sloppy way oversized throats.

0to60
June 12, 2011, 10:52 AM
The reason I asked this question in the first place is because MBC makes kind of a big deal about choosing the right BHN and how to do so mathematically. If I am to "eyeball it", as most of you are doing, then I can save myself some $$$ and order from mastercastbullets. The thing that was holding me back was that MBC seemed to imply that 18 was the correct BHN for the 200 gr SWC round that I like. But if I can get away with BHN 14, then my next order will be from mastercastbullets.

Galil5.56
June 12, 2011, 11:40 AM
If the fit and lube is good for the application, I'd go for the BHN 14 option from your caster of choice using loads, loaded to normal .45 ACP working pressures. I have cast and shot a ton of 200 grain LSWC's, using nothing but air cooled wheel weights that are a lot softer than BHN 14, using a lot of different propellants and pressures, and the results when properly sized and lubed are fantastic. As I said in my first post, fit to the barrel and proper lube used in my experience maximizes accuracy, and minimizes lead fouling.

Why I would choose mastercastbullets.com is because I'm sure Mike would gladly send you some no cost samples to make sure they are what you want, and then if you do order them and find them not to your liking, here is a quote from his site:

"RETURN POLICY: Money back for all unused bullets. MASTERCAST pays return shipping and will refund the shipping charges you paid to have the bullets sent to you."... How can you beat that?

Second reason I would choose Mastercastbullets.com is the savings is as you know huge compared to other suppliers I have seen for a shipped to your door price for the same bullet/alloy, especially if you only order 500 bullets which gets shipped for $5.25 plus insurance.

918v
June 12, 2011, 12:49 PM
Leading is caused by alot more than BHN. Bullets, contrary to popular belief, do not slide on top of the rifling. They do not need to obturate the bore to not lead.

When a bullet is sitting in the chamber, the nose part of the bullet sits in what's called the freebore. That is the part of the barrel without rifling. This freebor is often .001" to .002" larger than the groove diameter. Upon ignition, and before the bullet enters the rifling, the case unglues itself from the bullet shank and hot gas begins to spread throughout every bit of airspace inside the chamber. Since gas travels instantaneously at 7000 FPS and the bullet has to accelerate to 1000 or so FPS, you can imagine the gas will overtake the bullet in the freebore and force itself down the barrel, cutting off lead in the process. This is one of the ways leading occurrs.

This is where BHN comes in: As ignition begins, the base of the bullet gets hammered with a wall of gas. A soft alloy will immediately deform (obturate) when hit with that force. So a soft bullet sitting in the freebore .001" larger will deform and fill that .001" gap, thereby sealing the system.

A hard alloy, on the other hand, will not deform as much and may not seal the freebore. The gas, then, has the opportunity to escape around the bullet and cut lead off the shank in the process, and deposit it in the barrel. Typically, this will lead the first inch of the barrel.

Now, you can use a bullet that is at freebore diameter and it will not need to obturate. But such a bullet is difficult to chamber. You can't push a .453" plug into a .453" hole very easily.

Or you can use a softer bullet.

Or you can change the load for one that will generate higher startup pressures, but you have to be careful here. It is not the peak pressure that is important, but the initial starting pressure. In some loads peak pressue does not occurr until the bullet is well down the bore. We need the pressure right before the bullet starts to move. Fast burning powders like Bullseye are our friend.

I have found revolvers to be more sensitive to this variable than autos. Maybe this is due to their longer jump to rifling and the forcing cone. My 1911's shoot 22BHN Lasercast bullets just as well as 12 BHN Missouri bullets with the same mild 4gr Bullseye powder charge. My S&W 625 leads like crazy with the Lasercast bullet, though, and the accuracy sucks.

Here is a thread from rec.guns that people should memorize:

From: njohnson@marlin.nosc.mil (Norman F. Johnson)
Newsgroups: rec.guns
Subject: Re: [Reloading] How fast for hard cast?
Date: 2 Feb 1997 10:56:44 -0500

Jeff,

# I was reading the current issue of Handloader, and one of the writers
# was commenting on hard cast lead bullets. He stated that most bought'n
# hard cast bullets are so hard that they do not obturate (upset to fit the
# bore) well at 1000 f/s or less, and can lead even worse than swaged
# slugs. Which brings up the question (which he thoughtfully didn't
# address), how fast is fast enough for hard cast bullets?

He was absolutely correct:
Excerpt from "The Fouling Shot" Issue #81, Sep-Oct, 1989 "Match
Wheelgun and Load Preparation, page 81:
Correct bullet hardness for revolver target loads is about
8-12 BHN, depending upon the charge giving best bullet stability
and the chamber pressure generated.
The usable maximum chamber pressure of an alloy is a
function of its Brinell Hardness Number. As a rule of thumb,
optimum chamber pressure for adequate obturation without leading
is about four times yield strength. The conditions of firing in
a revolver are more severe than in a rifle, so this figure must
be taken as an absolute, though in a rifle this approximation can
be exceeded to about 5 times yield if everything is "perfect."
Within the range of alloy hardness we use for typical as-
cast or heat treated bullets (from 5-30 BHN), yield strength is
approximated by the BHN multiplied by 480. This means that a
soft alloy of 8 BHN, such as factory swaged lead bullets will
stand up to about 15,000 CUP (8x480x4=15,360), and an alloy of 12
BHN will stand 23,000 CUP.
This corresponds to the pressures generated by 4-6 grains of
fast burning pistol powders such as Bullseye, 231, Red Dot, Green
Dot or 452AA, which are all well suited for the .44 Spl. My
favorite all-purpose alloy is a mixture of indoor-range backstop
lead (mostly .38 wadcutter and .22 rimfire bullets) mixed with
about 1 part in 20 of Linotype to provide some minimal tin to
improve casting. This stuff makes a nicely filled out, soft
bullet of 11 BHN. Eric uses a similar alloy for his gallery
pistol loads. By the way, this soft alloy also shoots well in
moderate .30 cal. rifle loads up to about 1500 f.p.s., and is
without peer in the big bores, such as the .45-70.
The rest of this article is jamb-packed with other valuable tips
for improving revolver accuracy. It is posted in an effort to
convince you to become members of the Cast Bullet Association.
It's newsletter, The Cast Bullet, has more immediately usable
information in it in any given issue than ALL other gun periodi-
cals combined -- guaranteed! A great deal of the articles apply
to jacketed bullets as well as cast.
***************************************
VELOCITY REQUIRED TO EXPAND OR DEFORM VARIOUS HARNESSES
MINIMUM
TERMINAL HOLLOW *
BHN VELOCITY POINTS
*** ******** ******
30-50 2400 fps NR
20 2200 NR
18 1900 NR
14-15 1500 NR
10 1400 900 fps
8 1300 800
5(pure lead) 1200 700
NR - Not recommended for game shooting because of extreme
destructiveness. Good for varminting, though.
* - Hollow point size and bullet nose shape affect required
terminal velocity greatly, so these can only be considered
approximations. Hollow points are best used with pure lead or
tin-lead alloys as even small amounts of antimony cause bullet
break-up. If antimonial alloys are used, do not exceed 1 1/2%
antimony or 10 BHN.
***********************************
The 1991 Jan-Feb issue of the Fouling Shot has an article by O.H.
McKagen and Dennis Marshall entitled "On Lead-Tin Solders", page
89-8 through 89-14. It is the best explanation of bullet alloys,
their hardening, softening, time dependent characteristics (no,
that bullet that you cast last week is not the same bullet that
you have on your shelf today) that I have ever read. It puts
into perspective the nature of a number of alloys used for
cast/swaged bullets, time hardening, time softening, boundary
slippage etc., in words that the layman an understand.
The resulting knowledge can be used to give the caster/swager
more control over his bullets than he might have ever dreamed was
possible. It also helps one to recognize errors that often
appear in the glossy gun magazines when the writers presume to
relate their infinite wisdom to those (us) serfs who are
unread, unwashed -- you know the rest.
*********************************************************
ANOTHER CBA PITCH
There are a good many articles in the pages of the official
journal of The Cast Bullet Association that correct many of these
old errors.
Cast Bullet Association
Ralland Fortier
4103 Foxcraft Drive
Traverse City, Mich. 49684
$14.00/yr.

back issues, Index, etc. from:

Frank Stanard, Director of Services
7418 Ridgewood Avenue
Chevy Chase, MD 20815
***************************************
God Bless!
Norm

bds
June 12, 2011, 01:21 PM
I've read a lotta threads around here where folks are talking about their pet loads and whether they cause leading, and there seem to be a lotta cases where one guy says a load causes no leading, and another guy stopped using that load because it caused too much leading. So is this all a "your mileage may vary" thing?
I had a similar discussion at the range yesterday afternoon with two new reloaders who bought 1911s to start loading for.

It is my opinion that leading depends primarily on 5 factors:

- Bullet to barrel fit - Bullet diameter .001" over barrel (.452" diameter bullet vs .451" barrel)
- Bullet base's ability to deform to seal against the barrel - obturation
- Sufficient powder charge/chamber pressure to cause bullet base deformation - obturation
- Bullet lube type/performance - ability to liquefy and seal forward of the bullet lube ring yet form a solid gasket around the bullet
- OAL/leade/free bore/throat distance - how far the bullet has to "jump" from case neck to the start of rifling


Not all factory barrels have .451" groove diameter and some are larger. My M&P45 is .451" but the PT145 is .453". Missouri Bullet 200 gr SWC (18 BHN IDP #1) with 5.0 gr of W231/HP-38 don't lead the rifling in the M&P45 (just a light smearing at the chamber end and absolutely no leading whatsoever in stainless Kimbers) but leaded down the rifling in the PT145 and accuracy suffered significantly.

If you have over sized barrels, typical .452" diameter bullet may not provide tight enough seal and cause leading by (in sequential order):
- During the initial powder burn, hot high pressure gas travels faster than the bullet while the bullet jumps through the leade/free bore/throat (distance from case neck to the start of rifling) and turns some of the hard lube into liquid at the surface, but because of the over sized barrel, instead of sealing the bullet to the barrel, liquefied lube gets blown off forward of the bullet causing the bullet to be "naked".
- As powder continues to burn, hot high pressure gas causes "gas cutting" and bullet base erosion of now naked bullet softening the surface of the bullet.
- As bullet travels down the barrel, rifling do not "dig/grip" the softened surface of the bullet and strip off lead (this explains the long strips of lead along the rifling) instead of bullet's bearing surface gripping the rifling to rotate.


Leading caused by improper bullet to barrel fit will be aggravated by harder bullet (BHN 21-24) as bullet base will deform less and more hot high pressure powder ignition gas will leak around the bullet. For the PT145 oversized barrel leading issue, I thought about ordering oversized bullet (.453") but I wanted to keep the same diameter bullets in stock. My leading issue with PT145 was addressed by using softer 12 BHN 200 gr SWC (Bullseye #1). The softer bullet deformed well with the 5.0 gr of W231/HP-38 charge and now leaves a light smear at the chamber end. Even the lighter recoiling 4.0 gr of Promo/Red Dot charge works well now in the PT145 and accuracy also improved (of course, the 12 BHN bullet shoots fine in M&P45 and Kimbers with no leading).


Bullets, contrary to popular belief, do not slide on top of the rifling.
Very true. With proper bullet-to-barrel fit, deformation of bullet base and proper lube type, bullet slides on liquefied film of lube (http://www.thehighroad.org/showthread.php?p=7299835#post7299835) much like car's engine parts moving on a thin film of oil that prevents metal-to-metal contact.


I also looked at the BHN "formula" but moved away from using it as a sole determinate to reduce leading as there are many production variables that exist like leade length (can you say Glock?), rifling type and height (rounded hill/valley of Glock), barrel groove diameter, OAL and lube type.


All in all, based on my experience with MBC bullets in 18/12 BHN, I now use more simpler guidelines:

18 BHN bullets:
With proper bullet-to-barrel fit (.001" over), I can use mid-to-high range lead load data (or reduced jacketed load data) with no leading or minimal smearing at the chamber end.

12 BHN bullets:
With proper bullet-to-barrel fit (.001" over), I can use start-to-high range lead load data (or reduced jacketed load data) with no leading or minimal smearing at the chamber end.

With oversized barrel situation where groove diameter is same or larger than bullet, I can use mid-to-high range lead load data (or reduced jacketed load data) with no leading or minimal smearing at the chamber end.

For me, even the higher pressure 9mm/40S&W loads work, even down to start charges. Yesterday afternoon, 300 rounds of 9mm 125 gr RN (18 BHN SmallBall) were shot with lighter 4.0 gr charge of W231/HP-38 at 1.120" OAL loaded for my daughter (I usually prefer 4.2-4.3 gr). This is essentially the start charge according to Hodgdon (125 gr LCN 3.9-4.4 gr at 1.125" OAL) yet the load reliably cycled the slides on G22/G27 using Lone Wolf 40-9 conversion barrels and ejected spent cases behind me and to my right. Few strokes with copper bore brush dipped in Hoppes #9 solvent showed very light smearing at the chamber end that was removed with 3-4 strokes with old copper bore brush wrapped with copper scrubber strands (Chore Boy).

I get the same results with 40S&W 180 gr TCFP (18 BHN IDP #5) loaded with 3.8 gr charge of W231/HP-38 at 1.125" OAL that my wife likes to shoot out of G22/G27 (factory or Lone Wolf barrel). I prefer to shoot this bullet with 4.0+ gr of W231/HP-38 out of M&P40/G22/G27 as the sharper recoil matches the recoil of my 155/165 gr jacketed match loads and brings the front sight faster back on target.

Walkalong
June 12, 2011, 02:54 PM
If the bullets fit the groove diameter, but are smaller than the throat/freebore in an auto, they can lead if the bullet does not get hit with enough pressure to obdurate and seal the throat. It will lead much worse if it is undersized for the groove diameter as well.

Just like a bullet needing to fit the throats on a revolver, but not nearly as critical.

USSR
June 12, 2011, 04:22 PM
...200gr LSWC over 5 grains of Bullseye, 900 fps at 20k CUP.

I'm currently using an alloy with a BHN of about 9 for this very same load.

...158gr bullet out of a .357 magnum should be around 1300 fps

Given a choice between using 158gr bullets with a BHN of 12 or 18 with a 14gr of 2400 .357 Magnum load, I would select the 12 BHN bullets every time. Commercial casters push the high BHN bullets, but with a proper fit to your gun, they are seldom necessary. Just MHO.

Don

627PCFan
June 12, 2011, 09:46 PM
It might be an extreme example but Im running MBC 357 180 Grain Strikers in my 336 35 Remington with a max charge of h-322.....and not even a remote sign of leading. The only leading i have gotten with any of their bullets was using 18BHN in a slow 38 special. That took some scrubbing.

Gadzooks Mike
June 12, 2011, 10:19 PM
I have previously exchanged some emails with Brad about this, and there is a mistake on his web site concerning that formula. Simply put, he uses CUP and should be using PSI.

In the emails, Brad said he had obtained this info from here: http://www.lasc.us/Brennan_3-3_CastBulletHardnessRequirements.htm

You will notice that those formulas use PSI, and they use psi for a reason. BHN is measured using metric units - kilograms of force per square milimeter. If you multiply that by 1422, you convert it to PSI - pounds per square inch. Please not that CUP is not equal to PSI.

Interestingly, Brennan goes on to say that because data falls outside of the formulas, he doesn't believe the theories are correct.

As an aside, if you want to convert between CUP and PSI, this will get you a good approximation, but is NOT exact:

CUP = (PSI + 17,902) / 1.516
PSI = (CUP * 1.516) - 17,902

evan price
June 13, 2011, 05:09 AM
I used to be one of the harder=better believers myself until I started casting my own. I load for everything from 32 Long to 44 Magnum. I shoot 32 Long, 38 Special and 45 ACP around 800 fps and 357/44 magnum at 1000 fps and the 357 Mag and 44 Mag up to 1500 fps all with lead. I use water quenched range scrap which is around 12bhn for the slower velocity stuff (1000 fps and under) and save my wheel weights +tin for the Magnums at around 16 bhn. The most critical thing was to make sure I was sizing correctly. I normally tumble lube in ALOX and let it dry, use a Lee push-through sizer and then tumble lube again.
I found out totally by accident (I lubed and forgot to size a batch of 9mm) that my bore was bigger than I thought. My 9mms were leaving lead at the chamber end but clean further on. Turns out using a .356" sizer was the trouble. Unsized my 9mm mold drops around .358" but they are not concentric. I switched to a .357" sizer for 9mm and presto, no leading. .356" was the 'standard' for 9mm so I used that at first. I finally slugged my barrels and found the Sigs are a .001" larger than I thought they were.

Now I size everything .002" over nominal (.358" for 38/357) and shoot the 44 Mag and 32 Long as cast (which is .315" for the 32s and .431" for the 44 mag) and that was what did it- softer lead, slightly oversize, and ALOX tumble lube.

0to60
June 13, 2011, 09:08 AM
I have previously exchanged some emails with Brad about this, and there is a mistake on his web site concerning that formula. Simply put, he uses CUP and should be using PSI.

Very interesting. MBC says in the article, "This pressure is measured in “copper units of pressure” (CUP) and expressed in thousand of pounds per square inch."

And then he still gets it wrong? At this point, I'm finding MBC's webpage on this stuff to be incorrect enough to warrant taking it down.

Why am I being such a stickler? Because I didn't realize reloading was MUCH more art than science. When a bullet manufacturer goes into detail and gets mathematical, it grabs my attention. To find out that the information is incorrect, well, that makes me lose a lotta faith in the manufacturer's understanding of his product. Right now, I feel like a guy who bought a product and then went home and found that much of what the salesman told him was totally incorrect. I'm not saying MBC doesn't make a great bullet, they CERTAINLY do. But one should prolly base his BHN requirements on personal experimentation, not MBC's claims.

USSR
June 13, 2011, 10:24 AM
...I didn't realize reloading was MUCH more art than science.

Truer words have never been spoken.

Don

Gadzooks Mike
June 13, 2011, 09:16 PM
I didn't realize reloading was MUCH more art than science.

I don't think it is, I just think we don't understand all of the science involved. I think we've got a good handle on most of it, but not all. I'm not sure we will understand it all completely until we get some high-speed cameras inside the chambers.

MissouriBullet
June 14, 2011, 08:32 AM
There is both art and science to this and also, where they meet, there is voodoo! :-)

Gadzooks, you are absolutely correct about P.S.I. versus C.U.P. This is one of those "to-do list" things that I need to correct.

Oto, I actually didn't state that going with the correct hardness would result in no leading, rather, that leading can be minimized this way. As has been pointed out by the wise folks here, other factors are very important in this equation, especially bullet/barrel fit, which is the most important factor in my opinion.

I used the 5.0 grain Bullseye load as an example and used round numbers to exemplify the concept. Other powders will create more pressure, some less. But it serves as a good example on how to do the calculation. And also, I was reporting on customers' experience, taken from this very forum, when I mentioned the 1450 fps/no leading. I don't actually own a .357, myself.

You mentioned that I made a big deal about the hardness, well, that would be because that is the only real variable that we can control and so that is what we focus on. If you would visit our Facebook page (linked to from our website) and look at the Discussion area, you will find more specific information that what I put up in the Technical article on the main page.

But that said, obturation IS important and can compensate to some extent for an oversized bore and, all things being held equal, it will minimize leading.

Brad

Walkalong
June 14, 2011, 09:01 AM
Every once in a while someone comes along who understandable thinks we can lay out everything about leading in a scientific way so that we can figure out in advance what alloy or BHN we need for a certain application.

They soon find out there is no magic formula, or set BHN number for any given application.

There are so many variables in alloys, BHN, hardness, how ductile it is, dimensions and smoothness of throats and bores, peak pressure, pressure duration, powder speed, etc, etc, that each case has to be tried on its own.

We do have some very good proven facts that help us formulate a load that "should" work without leading in a given application, and then help us eliminate any minimal leading if we get it.

But yes, there is art to it, as well as science. :)

bds
June 14, 2011, 10:18 AM
When I transitioned from 21-24 BHN hard cast bullets to Missouri Bullet with 12-18 BHN, I found these articles by Glen Fryxell (http://www.lasc.us/ArticlesFryxell.htm) to be quite enlightening:


Cast Bullet Alloys and Obturation - http://www.lasc.us/FryxellCBAlloyObturation.htm
... there's not really much need for ALL cast bullets to have a Brinell hardness of 24 ... In fact, these hard bullets may well be inadvertently causing leading. How? These commercial alloys are commonly too hard to "bump up" (or obturate) and seal the bore at typical revolver pressures. The resulting blow-by of the hot gases past the bullet's bearing surfaces can leave significant lead deposits in the barrel.


A Few Comments on Cast Bullet Alloys - http://www.lasc.us/FryxellCommentsCBAlloys.htm
There are very, very few revolver applications that require a BHN of over 20. In my experience, revolver leading can almost always be traced to some other factor (inadequate lubrication, improper sizing, barrel/frame constriction, etc.). Only very rarely is barrel leading caused by the bullet being too soft. In support of this claim, let me point out that many muzzle loaders prefer bullets cast from 30-to-1 alloy (which is quite soft, BHN of about 9) and these smokepole slugs are routinely driven to 1300-1400 fps. In addition, high-velocity .22 Long Rifle ammo uses an even softer bullet at over 1200 fps (and if a .22 leads, it's a gun problem, not an ammo problem). Elmer Keith's favorite cast bullet alloy was 16-to-1 lead/tin, which has a BHN of only 11. This is the alloy that gave a roaring birth to the .44 Magnum using plain-based cast bullets loaded to 1400+ fps. Properly loaded and lubed, Elmer's alloy will leave a magnum revolver barrel shiny and clean after a long day shooting.


Lubricating Cast Bullets - http://www.lasc.us/FryxellLubeCastBullets.htm

Undersized cast bullets leave a gap between the bullet and barrel, leaving them unable to restrict this pressure-induced lube flow. As a result, the lube very quickly gets blown out of the barrel in front of bullet, leaving the bullet "naked", un-lubricated and unprotected. This phenomenon is especially problematic with the hard lubes; once molten, the low viscosity liquid lube gets blown out rapidly if the bullet is undersized.

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