Hardness formula & Missouri Bullet


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BaltimoreBoy
October 27, 2012, 11:54 AM
Nooby question:

Mo Bullet gives a little formula on their site where they suggest that dividing CUP by 1280 to get an appropriate hardness. (I know CUP isn't exactly pressure)

They offer their .358 bullets in BH of 12 or 18

This puzzles me a little in that in 38/357 arena
17000/1280 = 13.28
20000/1280 = 15.62
23040/1280 = 18
30000/1280 = 23.43

So, does this mean that:

For all except very light target loads the BH 18 is the more appropriate?

That one can't even approach real magnum velocities with BH of 18?

My loading data shows that one can drive 158 grain lead up to almost 1200 fps. But does that mean that I need BH 22 to do it without excessive leading?

I guess I'm also asking, Is this formula good? And what hardness is preferred by the experienced lead loading 38/357 reloader community?

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bds
October 27, 2012, 12:48 PM
Missouri Bullet ... They offer their .358 bullets in BH of 12 or 18

So, does this mean that ... one can't even approach real magnum velocities with BH of 18?

My loading data shows that one can drive 158 grain lead up to almost 1200 fps. But does that mean that I need BH 22 to do it without excessive leading?

Is this formula good?
Glen Fryxell covers BHN formula/velocity/leading in his articles (http://www.lasc.us/FryxellCBAlloyObturation.htm), chapter 3 (Alloy Selection) (http://www.lasc.us/Fryxell_Book_Chapter_3_alloySelectionMetallurgy.htm) and chapter 7 (Leading) (http://www.lasc.us/Fryxell_Book_Chapter_7_Leading.htm) of his book:

Obturation is the plastic deformation of the cast bullet alloy due to the force of the expanding gases on the bullet's base ... cast bullets do indeed obturate, given that the alloy is appropriate for the pressures generated.

In the intervening years, extensive experimentation has revealed the empirical correlation of 3 x 480 x Brinell Hardness Number (BHN) (or more simply, 1440 x BHN) as an estimate of the minimum peak pressure required for bullet obturation ... Thus, a bullet with a BHN of 24 (typical of commercial hard-cast bullets) will not undergo plastic deformation and obturate until pressures exceed 34,000 psi.
http://www.thehighroad.org/attachment.php?attachmentid=173921&stc=1&d=1351356448
Standard revolver loads. For this category, a Brinnell hardness of 11 to 12 is desired ... Included in this group are the +P loads (up to about 20,000 psi and 1100 fps).

Magnum revolver loads. The target hardness here is generally something in the range of 12-18 BHN ... Brinnell hardness of about 16 is useful up to about 1700 fps.

Leading caused by the bullet. The cause of leading can be traced to the bullet if it's the wrong hardness for the application, the wrong size for that particular gun ... a bullet that's too hard (e.g. BHN 22) can fail to obturate, and lead the trailing edge of the lands.

This is a common problem with commercial hardcast bullets pushed at intermediate velocities. The bullet can also be the source of leading if it is sized too large (lead build up in the forcing cone) or too small (coated over the entire bore).

mdi
October 27, 2012, 01:36 PM
FWIW; Fit is more important than bullet hardness, IMO. Size your bullets to fit your gun and 90% of leading problems go away. I cast and shot 12 years before I read about the "formula" and I was able to work out my leading problems by making sure the bullets fit the gun they were used in (six revolvers and 4 semi-autos). I cast plain old wheel weight alloy for all my guns including some hot .357 Magnum and .44 magnum loads...

Mebbe ignorance is bliss? :cool:

bds
October 27, 2012, 01:54 PM
I cast plain old wheel weight alloy for all my guns including some hot .357 Magnum and .44 magnum loads...
Perhaps your .357/.44 Mag loads worked along with proper bullet fit because you were already using the proper bullet hardness?

Plain clip on wheel weight is 12 BHN and water quenched wheel weight is 18 BHN - http://www.lasc.us/CastBulletNotes.htm

http://www.thehighroad.org/attachment.php?attachmentid=173932&stc=1&d=1351360428

GP100man
October 27, 2012, 02:14 PM
The boolit must fit first !! Hardness gives it strength to withstand hitting the cone & grabbin the rifling at a higher velocity .

My wadcutter alloy checks at 8bhn , but the booilt is 359" I have no problem until I over speed the alloys ability to grab the rifling .

In my opinion shooting bhn18 booilts for target work is a waste of alloys, I learned this the hard expensive way !!

If boolits are undersized ANY it will not matter how hard they are they WILL lead the barrel heavilyfrom stem to stern !!!

CZ57
October 27, 2012, 06:21 PM
Simple answer: use the 18 Brinell with the 158 to achieve 1200 FPS or higher and look here for good data. www.ramshot.com ;)

BaltimoreBoy
October 27, 2012, 07:18 PM
Thank you gentlemen, you have put my mind at rest.

Walkalong
October 27, 2012, 08:02 PM
look here for good data. www.ramshot.com;) (http://www.ramshot.com/)

Or try one of these. ;)

http://www.alliantpowder.com/

http://www.accuratepowder.com/

http://data.hodgdon.com/main_menu.asp

http://www.imrpowder.com/pdf_reload.html

http://www.lapua.com/en/products/reloading/vihtavuori-reloading-data

bds has you on the right track.

USSR
October 27, 2012, 10:05 PM
FWIW, Elmer Keith developed the .44 Magnum using bullets with a BHN of 11. The idea that you need a revolver bullet with a BHN of 18 for a .357 Magnum load is ridiculous. As previously stated, it's all about fit.

Don

41 Mag
October 28, 2012, 08:14 AM
While I have shot a few commercial cast bullets, the majority of them were Oregon Trial, and the remainder were Zero HBWC's.

With the OT I used their 158gr RFN from both of my .357's with top end loads for hunting hogs, and with the Zero's I simply loaded light target loads for my .38 SPL.

Sine early last year I have been pouring my own from several different alloys. Initially I used straight WW both air cooled and water quenched to determine which one of them would be more suitable for loading in my 454. Granted I AM using a GC designed bullet, but I have run them with and without the GC with the same load and not found much difference in performance with regards to leading. I will say that the GC does show a marked improvement in accuracy however.

My WW alloy when tested for hardness usually runs between 10 & 13, depending on how long it sits after pouring and at what temp I poured it at. The longer the harder. I normally usually wait two weeks minimum after pouring before I size and load as this appears to be about the apex of the hardening. That said if allowed to sit another couple of weeks or longer they will creep up a bit harder also due to the temp at which they were poured. If I kep things at around 675 degrees for that particular bullet, they usually stabilize right at a 12 BHN.

What is posted above it a great general rule on using the proper alloy for the proper pressures with out a doubt. However it IS a general rule, and you cannot count on the WW alloy to be as consistent as it one might have been. The older the weights the more uniform they might be as in the later years cost contributed to ingredients and the overall alloy might contain any number of things besides the lead/tin/antimony it once did and also in more or less equal proportions.

As mentioned your fit will be the best determining factor in how well a particular bullet or alloy will preform in your handgun. Using the list above you might try something running both in a 12 and a 15 BHN with the proper fit to your barrel. Usually this is around .001 bigger than the actual bore dimension which is take using a pure lead slug driven through and measured using a mic, across the widest points of the resulting lands on the slug.

Once you have your overall dimension then your ready to order your bullets. If after you start out loading you see leading in your barrel it can be from one of several things. The number one thing is wrong size, followed by not enough pressure, followed by the lube isn't cutting it. The first one is pretty easy to determine, and eliminate, the second one usually will start off with the lower end loads but gradually get better as you work up. Sometimes it might take switching to just a touch quicker powder but even so you can see the diminished leading s you work up with what ever you start off with. The issue with this is some powder has a VERY narrow range in which to work, which is why Unique and 2400 type powders are so popular with lead bullets, where as H110/296 isn't.

As for the lube issues, most commercial cast bullets use a hard lube which will stay put during shipping. Not to say it isn't a decent lube, but sometimes just not right for the given situation. You can easily check this by tumble lubing a few rounds using Lee Alox which runs about $7 per bottle or so, and is plenty enough to do a couple thousand bullets if used properly. If you see the leading go right away which has been seen many times you know that the lube is the issue, however you have to only change one thing at a time.

Leading isn't a major issue unless it is so bad it fouls the rifling or is blowing the accuracy out in only a few rounds. If there is only a minor amount showing up after say 10 rounds but stabilizes and doesn't get worse I wouldn't sweat it. My 454 has one spot in the barrel where I can see a small smear appear after the first round, but after 50 it hasn't gotten any bigger, and I run them at 1550fps+. My 41 mag, the very first cast loads I shot through it years ago, had strings of lead hanging out the muzzle after only three shots and took a week of scrubbing to get it all out. Never got those bullets to shoot in it either.

So my best advice would be to first slug your barrel or have it slugged by one of your local gun smiths if your not comfortable driving a lead slug through your barrel. Also you need to verify the dimensions of each chamber mouth on your cylinder, as sometime these are not all the same size and sometimes they ARE smaller than the actual bore on your revolver. If they are you will never get cast bullets to shoot properly without seeing quite a bit of leading. The chamber mouths all need to be right at, or just a touch bigger, than .001" of your bore diameter for best results. One other area to look closely at is the area right where your barrel screws into your frame. Sometimes there is a restriction there caused by the barrel being screwed in overly tight. This can be removed usually by running some of the lapping compound coated bullets through with medium loads. Once you get it gone, you should be fine.

I only bring these things up because they are and have been real issues that folks have dealt with. They are things that if found right off the bat will relieve you from hour of scratching your head. Whether or not they actually exist in your revolver is always an unknown until it has been slugged. This is why so many folks recommend slugging your bore first. If you know up front you have issue in one or more areas, and correct them then you are miles ahead with not only cast bullets but your standard jacketed loads as well. You will see a marked increase in accuracy from both if everything is of the proper fit from start to finish.

I realize this was long and drawn out, but I have been through some of this first hand, and know it can make or break you from shooting cast. Cast bullets are cheaper, especially if you pour your own, and they will preform as good or better in most cases than anything jacketed on the market, as you can taylor them to a specific velocity that you want to shoot at verses having to drive them as hard and fast as you can to get them to preform.

Just as an example what velocity you you say you would have to drive any of your favorite jacketed bullets to, to deliver repeatable performance like these cast HP's,
http://i49.photobucket.com/albums/f285/41nag/Shooting/Cast%20Boolit%20Loading%20and%20Shooting/Alloy%20Testing/0908121154a.jpg

The answer is just about 1000fps on the nose, the initial weight before firing was between 265grs and 277grs depending on which bullet. The end weight results was a loss of no more than 15grs overall no matter the initial weight. To me that is performance much better performance than I have seen with ANY jacketed bullets I have ever tried in some 40 years of loading. This isn't to say I threw in the towel on jacketed as they DO have a use, but for my handguns I have found that many I have sitting on my shelf will simply continue to sit there as I find more and better loads and results with cast.

Hope this didn't bore you to tears and it sheds a little bit of light on cast in your revolver.

BaltimoreBoy
October 28, 2012, 05:44 PM
Thanks again gentlemen.

"I realize this was long and drawn out..."
Not at all 41Mag - most informative.

918v
October 28, 2012, 06:37 PM
You should get the 12BHN bullets and try the harder ones only when the soft ones give you problems, i.e. like leading at high velocity in rifle length barrels or inaccuracy with a particular powder/primer combo you have your heart set on.

BaltimoreBoy
October 29, 2012, 09:54 AM
"...get the 12BHN bullets and try the harder ones only when the soft ones give you problems, i.e. like leading at high velocity in rifle length barrels..."

918v: That's pretty much what I had concluded from the preceding discussion. Thanks for the comment about rifle length barrels - I may be looking to try some rounds in a carbine as well as a revolver.

Hondo 60
October 29, 2012, 10:41 PM
I use the BHN12s for .38 Spl & really wimpy .357 mag loads.

The 18s - (MBCs .357 Action) are used for full .357 Magnum loads.

evan price
October 30, 2012, 06:49 AM
Size and fit are just as important- maybe MORE so- than hardness of the alloy.

My rule of thumb is velocity divided by 100 gives you BHN.

Running 1200 fps/100 = 12 BHN (when properly sized).

So far that's never failed me.

I used to be a member of the HARDER = BETTER camp. Then I had an epiphany, actually LISTENED to the old timers, and now I don't worry so much about hardness, and I get nearly zero leading with soft bullets, whereas hardcast commercial bullets got me leading. Sounds counterintuitive but it really isn't.

My mixed range lead runs right between 8-10 bhn and water quenches around 12 bhn. Works great in anything I load it into, including 44 mag and 357 mag target loads around 1200 fps max.

Fatelvis
October 31, 2012, 08:09 AM
The boolit must fit first !! Hardness gives it strength to withstand hitting the cone & grabbin the rifling at a higher velocity .
I agree with this. Way too much emphasis is placed on hardness. Make sure the boolit fits the bore properly, and wheelweights will work great for most of your shooting. If you want to really push them fast/hard, use a gas check on a wheel weight boolit.

bds
October 31, 2012, 09:48 AM
Believe me, I am a fan of "bullet fit to barrel".

However, I load for multiple pistols of family, relatives, friends, neighbors who often join me to the range and my loads must work in all of their pistols with varying barrel groove diameters, ramp shapes/angles and chambers - so I use a single bullet diameter, OAL, hardness, powder/charge that work well in all the pistols.

Even just for my multiple pistols, having different sized diameter bullets is out of the question - imagine grabbing the larger sized bullet loads for smaller diameter barrels? It will be FTF/jam-o-matic at the range! :fire:

Having the right bullet size for the barrel is ideal (.001" over groove diameter) if you only have one pistol for the caliber, but if you have more than one pistol or need to load for multiple pistols with different groove diameters, softer BHN and powder/charge combo that will properly deform the bullet base/obturate with the barrel is a must. My 45ACP loads using .452" sized bullets in 12 BHN will work well with different sized groove diameter barrels (.451" - .456"+) without leading the barrels. Besides, where can you find .458" sized 45ACP bullets?

Of course, if you choose to have different sized bullet loads for different groove diameter barrels ... that's your choice.

sean1129
November 6, 2012, 10:59 PM
For what it's worth, I've been down this road in my reloading questions and purchasing from Missouri Bullet Company. I've used the 12 and 18 BHN for the purposes listed on the MBC website. However, I've also used the 18 BHN in my Smith 686 for both 357 and 38 specials--I'm talking somewhere in the 3-4000 numbers, and in BOTH cases the 18 BHN is flawless--no leading, same accuracy, etc.

A local reloading store advised me many of these issues comes from the rifling cut in a barrel--they often need to be lapped for proper fit...

Just my $0.02.

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