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jonp
02-23-2013, 07:25 AM
I'm somewhat new to the cast boolits having stuck to Jacketed bullets up to this point so forgive a question that is probably common knowledge. I've read a number of threads relating to BHN and pressure but not on velocity. Is there a "rule of thumb" or chart that gives an approximate BHN for a cast as related to the max/min velocity that can be used with that bullet? The reason that I ask is that I bought some cast boolits from a manu that they say are BHN 10 and are ok up to 1400 fps but that seems to be over the recommended fps according to several sources I have read and will lead to leading.

Tatume
02-23-2013, 08:03 AM
According to Brian Pierce (Handloader 246, April-May 2007), BHN 11 is appropriate for 45-Colt level pressures (14,000 psi). For the range of pressures we use in magnum revolver ammo, hardness should be around 16 BHN.

Freedom Arms cautions that bullets used in the 454 Casull that are not sufficiently hard can cause cracking of the forcing cone. They recommend very hard bullets for full-power loading of this cartridge.

Larry Gibson
02-23-2013, 09:32 AM
BHN is only half of the bullets "hardness"; other half has no real measurement but is conceded to be "toughness" or malleability. Bullets with the same BHN can be completely different alloys and all can be driven to high velocity. How high a velocity w/o leading and with accuracy depends on the actual composition of the alloy, the lube used, fit, the condition of the firearm, barrel length, the cartridge used in and the burning rate of the powder used plus a few others probably.

Lets jus say (since you didn't mention) you have a 44 magnum Ruger BH with 7 1/2" barrel. Those commercial bullets with a BHN of 10 might do fine at 1400 fps with H110 or 2400 but may not with a faster powder.

The short answer is; no, there is no "rule of thumb".

Larry Gibson

btroj
02-23-2013, 09:36 AM
Lading is NOT solely related to hardness. Fit to the bore is far more critical than hardness for stopping leading. Want proof? Shoot hard, undersized bullets at low pressure in a handgun. It will lead.

Velocity alone isn't the key factor, pressure plays a large role. Pressure curve does also. A 1200 fps load with a. Fast burning powder may lead while the same velocity for a slow burner may not. Different pressure curves.

BHN 10 bullets could easily go 1400 fps, in the right load. I can do that in my 45-70 with no real problem. Try it in a 357 revolver and thing get bad quickly.

Fit to bore, and cylinder throats for a revolver, is most critical. Lube, bullet diameter, bullet style, bore condition, temp, pressure, powder choice, and many other things determine when something will or won't work.

My suggestion, take the bullets you bought and load a few up. Go try them. Only your gun can tell you if they will lead or not. That is the real test, do they work in YOUR gun? If they do, then they are fine.

felix
02-23-2013, 09:45 AM
Freedom Arms cautions that bullets used in the 454 Casull that are not sufficiently hard can cause cracking of the forcing cone. They recommend very hard bullets for full-power loading of this cartridge.

This comment does NOT go far enough. Should say: They recommend very hard bullets for full-power (anything over 35K PSI) loading of ANY cartridge in ANY gun. ... felix

Case Stuffer
02-23-2013, 10:02 AM
Casting,lubing ,sizing ,loading , cast Boolits is as much of an art as it is a science. If one reads all of the data in the Sticky threads here they will have a very good foundation to start with but still much to learn and very often with each new gun,powder,boolit,powder the fine tuning process starts all over again.

jonp
02-23-2013, 12:35 PM
Thanks for all of the answers, guys. The boolits in question are for a 9mm Auto not a revolver. I've loaded for my 44Mag and my 357Mag in cast for a number of years and have not had a problem but this is my first time trying for a 9mm and a 45ACP. The revolvers I've kept the speed down with medium loadings using cast for practice only but in trying for my auto's I've run into several problems and had the question about the velocity. I should be more concerned with the pressure and use that as a gauge rather than the speed, is that pretty much the consensus?

btroj
02-23-2013, 01:00 PM
9 mm can be a tough one sometimes. The case has a rapid internal taper and the case will often size the bullet base enough to make it undersized. This can mean leading. Usual remedy is a harder bullet.
45 ACP doesn't have that issue near as much and is easy as anything to get lead to shoot well.

The 9 mm may well do fine with those bullets, only the gun can say for sure. Give them a shot and see. You may want to seat a bullet, pull it, and see if the back end is sized down from the case.

In general pressure is a better judge of what BHN is required than velocity. It is caliber defendant too, however. Smaller diameter often needs harder bullets but there are no hard, fast rules. Each gun is a rule in itself.

CJR
02-23-2013, 01:04 PM
Ah the "Wonderful World of Lead BHN vs. Maximum Velocity Rule". I know it's fashionable to measure lead BHN and then multiply that BHN by 1422psi or 1492psi, or whatever, and then confidently state that's the maximum pressure the lead CB CAN take. Unfortunately, that Rule does not represent the real world of lead alloys nor is it verified by published scientific tests on ALL lead alloys. What is documented, by experiments and Physics, is the fact that ALL lead alloys have a stress vs. strain relationship which is non-linear in nature AND they ALL start deforming, 3-dimensionally, at LOW applied stresses. The deformation of a CB is suppose to be predictable by it's non-linear Bulk Modulus of Elasticity, which is a three-dimensional change in its volume and not a linear BHN relationship.

So what does this all mean regarding our beloved CB? Well if we apply the "BHN vs. Maximum Velocity Rule" and desire to drive a PPCB at 3000+ fps (~50,000 psi) we would assume we MUST use linotype or monotype or sterotype to achieve 3000+ fps. Then we conclude that these hard CB can only be used for targets and not game. However, in the real world, that's not the case. In reality a well-fit PPCB, with BHN as low as 13 or 16, can be driven VERY ACCURATELY at 3000+ fps.

Years ago I gave up on using this rule or that rule recommended by "some expert". Now a days, I continue to ask myself "what do the Laws of Physics say?" Then I continue to verify those laws experimentally by sending lot's of rounds downrange. Not only is this approach enjoyable but it seems to work well for me.

Time to exit, now that I've "rolled a grenade" into the room.

Best regards,

CJR

felix
02-23-2013, 01:19 PM
Well, no grenade. Just logic. ... felix

pls1911
02-23-2013, 01:43 PM
CJR,
I'd have agree on the points you make on your post, but feel most folks in the discussion are not paper rollers, but cast-lube &check-load and shoot types... Myself included.
Paper patching is an art certainly to be pursued if folks intend higher velocities, and I fully intend to try some with 45/70 rounds when I get around to it.
However, without the benefit of the paper patch, the aforementioned hardness/malleability and fit considerations would for the most part prevail.
For my pistols and rifle rounds I cast soft (about 9 bhn) with 50/50 pb/ww mix then heat treat and ice water quench to 23-26 bhn. Low antimony alloy, but very hard bullets will deform but not break up. And I normally size on the large side.
For me that works pretty well in weenie .38 loads through 2100 fps .30 cal gas checked loads, as well as all .45 or 45/70 loads, pistols and rifles.

1Shirt
02-23-2013, 02:53 PM
Seems like as usual, I agree with Larry G, no rule of thumb! Trial and error, and a bit of good luck doesn't hurt at all.
1Shirt!

303Guy
02-23-2013, 03:52 PM
I had a 44 mag once and I made up this wonderful hard a shiny alloy that cast real well. I also got some really crappy looking lead that cast fine but looked dull and pooh and was soft - too soft. I used the soft stuff for plinking and the 'good' stuff for sillywet. Then one day I recovered one of those pretty boolits and discovered they were being gas eroded down the grooves, leaving the rifling land impression about the highest remaining portion of the boolit. No rifling skid but it did explain the less than stellar accuracy which I was blaming on my shooting. (The boolit was recovered from soft soil almost undamaged). Those soft and uglys were the good shooters! Same powder charge - I used the slowest and bulkiest powder for the magnum (which also happened to be the only large pistol powder available to me, the equivalent of H4227).

geargnasher
02-23-2013, 03:59 PM
Too many factors to attempt to calculate or trend with any validity. I routinely load to pressures three times the 'ultimate compressive strength' of the alloy with excellent results. Not magic, just controlling the forces through design. It's all about finding balance.

Gear

DrCaveman
02-23-2013, 04:26 PM
Jonp

Do some searches on this site regarding 'leading' in your caliber of choice or any caliber for that matter. You will find extremely enlightening discussion which will take you weeks to read and absorb and then test.

I can't barely begin to explain it all, but for starters, it is a pretty unanimous consensus that the fit of the boolit in your gun's throat and barrel will be the most decisive factor affecting leading. Most everyone who has responded to your question here has contributed huge amounts to these discussions and you will probably be in for an eye-opener.

Here's one http://castboolits.gunloads.com/showthread.php?181724-Need-a-little-9mm-help&highlight=Leading+9mm

btroj
02-23-2013, 04:31 PM
Or do what I did. Cast, load, and shoot a bunch. See what does, or doesn't, work. You will become very adept at getting lead from barrels but will gain real, first hand knowledge.

Every gun is a new challenge. Some shoot cast easily, some fight you. Some defy all previous knowledge.

I have a Marlin 1894C in 357 that drove me nuts for 6 months. It didn't lead but it shot horrible groups. I tried all the loads that "experts" said worked well, in their gun. Finally got the right mould and now it shoots great. Tis gun needed to be fed what it wanted, not what other gun wanted.

Leading isn't a failure, it is a learning experience.

Eutectic
02-23-2013, 05:59 PM
The Section Density of your boolit........ This makes a very BIG difference on the velocity you can get away with. Low sectional densities can be shot faster than higher sectional densities for a given BHN...As in most things with boolits though... 'fit trumps all'.

'Fit trumps all' even over these 'yield' charts. Your alloy should 'yield' for optimum results... Can it over yield? Did I say 'fit trumps all'? I have shot .22 Hornet loads with an 8.5 BHN boolit at 2600fps at around 35,000psi. At better than one minute of angle accuracy I might add. But they fit like a glove and the Sectional Density of the boolit is low ... around .148.

Eutectic

303Guy
02-23-2013, 07:34 PM
Hornet with soft alloy? Mmmm ..... Actually, I just want an alloy that I can cast for the hornet!

jonp
02-23-2013, 08:55 PM
Thanks for the link, DrCaveman