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Thread: Where is BHN / Velocity real data located

  1. #1
    Boolit Mold Wish-A-Lot's Avatar
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    Unhappy Where is BHN / Velocity real data located

    I have spent months trying to get data that is corroborated in more than 2 places.
    I want to ensure obturation of bullets for various velocities and BHN's.
    Here is what I have for the most likely data.
    BHN * (3*480) = min. chamber pressure to ensure obturation.
    BHN * (4*480) = max. chamber pressure to ensure no deforming of the bullet.

    So, I have also noticed some people say add 1 to the BHN and then use the calculation for the maximum pressure.
    Some sites have stated max. BHN is BHN * (4*480)+10,000.

    I have cast .270 win. and, with a BHN of 22 driven them (G.C'd) at 2500 fps with a chamber press. calc. of 42,000 psi.
    The pressure is seen by the GC and the projectile is pushed forward but, what happens to the nose and body of the cast bullet.

    Has anyone done testing rather than passing on some information from others?

  2. #2
    Boolit Grand Master popper's Avatar
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    min. chamber pressure to ensure obturation That would be the pressure to expand the case and fill the throat with lead?
    max. chamber pressure to ensure no deforming of the bullet This one depends on boolit design. Of course a larger cal. will produce more FORCE at the same psi. From practical experience heat treated #2 or lino gives good performance @ 50K psi, GCd. Don't think you'll find the answer in a text book.
    Whatever!

  3. #3
    Boolit Grand Master Harter66's Avatar
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    I know a gentleman that has a game plan for some extensive testing with more than one high speed camera within the next 12 months to see first-hand exactly what a cast bullet looks like during it's bbl to free flight transition . His work will focus on 6.5 , 7mm and 30 cal from 2-3000 fps and twists from 8-16" . I expect that his tests will span 30-65 kpsi and bbls from 16-24" .

    Speer , Sierra and Winchester did some shadow photography in the late 40s through the 50s . I believe it was Winchester that found that their pointed soft point 180 gr 30 cal bullet was becoming a RN some where between the case and 15' out of the muzzle , probably under initial acceleration .

    I don't remember now if those photos were in the Lyman or Speer manuals .

    The point being that it isn't just something that happened/s to lead but jacketed and it is documented if you happen to dig at the right sore .

    I think the Lee manual has a pressure to BHN of known alloy guide . Any time you change the basic alloy either by accident or deliberate action it will change the formula . I used a lot of what was presumed 1-20 tin/lead sourced from tamper seals . It never occurred to me that I was also adding copper from the seal wire . As a result I have a great high speed stable alloy that handles 42-45 kpsi and expands on game . Added bonus it'll shoot 32-35 kpsi plain based . Lead let alone 75/25 WW-1-20 shouldn't do that . I suspect the copper is why so many do so well with range scrap .

    Physics plays heavily into this type of a discussion and I'm not qualified . Mechanically I can describe what happens .
    I'm not convinced that water cooled/HT lino is THE high speed solution .

    Early on I shot Red Dot in increasing loads until the groups failed then I shot the same bullet ,case , rifle with increasing loads of Unique then stepped in to rifle powders . In a particular 06' the RD would get about 1100 fps the Unique would go to 1400 fps and I could easily get 1700 with 4350 before I had bullet failure when applied to a 32 Rem and 30-30 both​ with much slower twist rates the results were the same except that 2200 fps was reached with 2" 100 yd groups with 4350 . At that time I was using straight WDWW and had no idea what I had actually accomplished or demonstrated to myself .

    BHN doesn't tell the whole story about how a bullet will behave under acceleration . A true lino bullet at 30 bhn won't do what a 90-3-7% lead tin antimony + arsnic 30 bhn does dissolve copper until the tin is saturated and it's not even similar . Introduce a babbit alloy to WW to reach the bhn and I don't even want to guess at what sort of behavior you might get . In any of these cases you may get exactly what you wanted or you may get a trade off that makes a poor target bullet great for cape buffalo but mediocre on paper or great on paper but wasted on anything bigger than a pygmy cotton tail . Don't hit the cottontail any further back than the eyeball cause poof .
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  4. #4
    Boolit Master Yodogsandman's Avatar
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    With so many valid personal variables, each shooter really needs to do their own "real world" testing.
    A deplorable that votes!

  5. #5
    Boolit Master
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    Actually, all the numbers you list are approximations. Bhn is in Kg/mm2 (that is mm squared). The pressure we use is lbs/in2 (or psi). The mathematical conversion from one to the other is Bhn x 1,422 = psi. That is very close to 3 x 480. What that means is that generally, the Bhn x 1,422 equals the pressure that the bullet metal will deform at (like the divot that forms when you test the bullet for Bhn).

    However, a LOT of other things make a difference when the bullet will fail other than Bhn. It is my opinion that that is a very good place to start when developing a load. In my experience, there is almost never a bullet failure when you use that equation. A bullet failure can be seen when the accuracy starts going bad. That usually happens long before leading occurs. However, with good lead, correctly sized bullets, throats, groove diameter, the speed of the powder, the quality of the lube, etc, you can usually (but not always) go to a higher pressure than you calculate with the above equation.

    When I increase the pressure, I don't ever remember getting to 4 x 480 as a good pressure, but I usually get above 3 x 480. I use it as a starting point and it cuts down on my experimentation a lot (not to mention not having to clean out leading from a mistake).

  6. #6
    Boolit Mold Wish-A-Lot's Avatar
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    I have never had leading when I use the chamber pressures and BHN limitations. I have gone into the 2,900 fps vel. range and don't know where the bullet hits hence my question on max. for BHN. The GC protects the base of the bullet but perhaps the trick is to have a hardness of 29+ for a BHN and make sure chamber pressures meet the min. For obturation.

  7. #7
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    Wish-A-Lot


    "I have gone into the 2,900 fps vel. range and don't know where the bullet hits hence my question on max. for BHN."

    While BHN/pressure does effect the velocity levels we can maintain accuracy with cast bullets at, in reality that relationship is not the deciding factor. As mentioned, bullet design, alloy composition and the rate of acceleration (controlled by the powder burn rate) have a much greater influence.

    The inability of your load to hit the target at 2900 fps probably had nothing to do with the BHN and probably not even the pressure (you don't say what rifle/cartridge/load was used). The total loss of accuracy was because of too much RPM. You probably were use a rifle with a 10" twist +/-(?) and at 2900 fps had severely exceeded the RPM Threshold. The RPM Threshold generally is in the 120 - 140k RPM range but can be lower and also can be pushed higher a bit. You want to shoot 2900 fps with a ternary alloy cast bullet and maintain accuracy you must control the RPM and keep it under 140k RPM. You aren't going to do it with a 10" twist barrel as you've found out.

    Here's what I do at 2900 +/- fps with a 164 gr 30 XCB bullet (NOE) cast of #2 alloy and simply WQ's. They have a BHN of 22 - 24. There's 20 shots there fired at 100 yards. The velocity for that load runs 2950 fps at 50,000 psi (measured in that rifle with and Oehler M43 PBL). There's 20 shots there, including the fouler out of the clean barrel, in 1.607". The 19 shots after the fouler went into 1.25". Given the 2nd shot was also out of the main group (that 2 o'clock hole) the remaining 18 shots that followed are very close to moa accuracy.......at 2950 fps;

    Attachment 197311

    If the barrel twist you used was 10" the RPM at 2900 fps was 220,400 +/-. The barrel twist I used was 16". I also used a very long barrel to gain that velocity accelerating the bullet slower using a slow burning powder (AA4350). The RPM of my load was 140,125 +/-. The difference in RPM is the reason you missed the target and I didn't. And no, your bullets did not disintegrate in flight. They probably did not lose stability either unless they were swaged down smaller than bore size and the lands lost their grip on the bullet (many confuse this occurrence with the lands "stripping" the bullet). W

    What happened was the 220k RPM had increased the centrifugal force on imbalances in the bullet and it either departed it's intended line of flight at a severe tangent or it began a helical arc trajectory that at the range of your target was larger than the target, hence they missed the target.

    With a 10" twist barrel using an appropriate cartridge, a properly designed cast bullet that fits the throat, a proper alloy, a suitable powder and using proper casting, preparation and loading techniques this is what can be expected.....if the rifle is accurate and you can shoot (no slam there but many think they can shoot accurately but in reality.........) to the ability of your rifle;

    Attachment 197312

    That is basically 10 shots into 1.5 moa at 100 yards at 2300+ fps out of a 10" twist .308W 24" barrel. That was with select 30 XCB bullets cast of a ternary alloy (#2). Pushing above that with those components and accuracy went south very quickly as the RPM was well above the RPM Threshold. Some add copper to the alloy and can do another 100 fps......maybe.

    The real test of a HV cast bullet to determine if the RPM Threshold has been exceeded is to shoot at longer range out to at least 200 yards but preferably 300 yards testing for linear expansion of the group size as the range increases. If your HV load holds 1.5" at 100 yards and 3" - 4" at 200 yards (use at least 7 shot groups as less really isn't statistically valid - use 10 shot groups preferably) the HV load has not exceeded the RPM Threshold. However, if that HV load shoots 1.5" at 100 yards and 4" to missing the target at 200 yards then it is exceeding the RPM Threshold. If the HV load is borderline you may have a large percentage of the shots within the expected 3" - 4" group size with only one, two or three shots that are non called "flyers". It is those "flyers" that are telling you the load is borderline exceeding the RPM Threshold. That's why a sufficient number of shots per group is necessary.

    At the end of the day () the BHN has nothing to do with why you missed the target at 2900 fps.

    Larry Gibson
    Last edited by Larry Gibson; 06-10-2017 at 10:17 AM.

  8. #8
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    the square mis-shaped lump of lead coming out the muzzle was the cause for missing the paper.
    wad cutter shapes don't fly stable over distance, and they especially don't fly stable when they are uneven on one side.

  9. #9
    Boolit Grand Master


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    Quote Originally Posted by runfiverun View Post
    the square mis-shaped lump of lead coming out the muzzle was the cause for missing the paper.
    wad cutter shapes don't fly stable over distance, and they especially don't fly stable when they are uneven on one side.
    The problem with that train of thought is that it is just a supposition. Some of us have actually gone to the trouble of recovering cast bullets fired at HV and have not found any to be a "square mis-shaped lump of lead".

    I have recovered five 30 XCBs fired with the load mentioned above in wet news print at 300 yards. None of them exhibited any such supposed deformation from acceleration. Lars and goodsteel recovered 25 +/- cast bullets fired from 1800 fps up through 2600+ fps out of a special bullet trap they made. None, nada, not a single bullet was a "square mis-shaped lump of lead". All the bullets they recovered looked just like they should have.

    As they say on Myth Busters.......that myth is "BUSTED"

    Wish-A-Lots problem at 2900 fps in not hitting the target was caused by too much RPM.......regardless of how much some wish to discredit the concept.

    Larry Gibson
    Last edited by Larry Gibson; 06-10-2017 at 12:19 PM.

  10. #10
    Boolit Master
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    To re-iterate what Larry says above, the relationship between RPM and accuracy becomes very obvious to anyone who tries to actually TEST the relationship, including posting targets of results achieved up to the RPMTH, compared to accuracy when exceeding same threshold.

    At any given twist rate, accuracy drops off sharply the moment the RPMTH is exceeded.

    This has been pointed out here numerous times, and it has been denied by the same people an equal amount of times. However, the latter have never posted as much as a smidgen of evidence.
    If the old threads still exists, go back and search the XCB project. That will tell you everything you need to know.

  11. #11
    Boolit Master
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    If the bullet is large enough diameter to begin one doesn't need any expansion to obturate.

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    they don't slump from the front to the back.
    maybe actually measuring those captured bullets would help.
    snow is the best declarant on the planet something they probably ain't got a whole lot of in Arizona.
    there is a whole other train of [proven] thought about designing a pre-slumped bullet and then not launching it with a bunch of 4895.
    look at the above example of switching to slower and slower powders to get part of the answer.

  13. #13
    Boolit Grand Master OS OK's Avatar
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    Applied physics 101 might be a good topic for a thread around here...

    That, and the 'Art of Posting of empirical evidence' with much less supposition...
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  14. #14
    Boolit Grand Master


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    original post deleted......it's just not worth discussing this topic with some members here......

    Larry Gibson
    Last edited by Larry Gibson; 06-11-2017 at 02:07 PM.

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  16. #16
    Boolit Grand Master OS OK's Avatar
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    Quote Originally Posted by Larry Gibson View Post
    original post deleted......it's just not worth discussing this topic with some members here......

    Larry Gibson
    I wish you'd reconsider that idea...some of us appreciate your detailed technical work, I know that you've been told that a number of times...there will always be the others to contend with.

    This forum is filled more and more with supposition and less fact every passing day. All that matters to most of these guys is..."How long does it take!"
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  17. #17
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    Okay.....

    "maybe actually measuring those captured bullets would help."

    All the recovered bullets were measured. That's how Lars, goodsteel and I have confirmed that lubed, naked cast bullets don't come out of the barrel at groove/bore diameters. They come out .003 - .005"+ under groove/bore diameter because they ride over a film of lube/fouling. Since liquids (the lube) aren't compressible (principle of hydraulics) the bullets are swaged down by that lube and yes, numerous lubes were tested (Lars makes them). If the bullet is not going to "lead" the barrel then there must be a film of lube between it and the bore.

    Those results are facts. They are the results of tests which were posted on this forum some time ago. There was also a thread started by another member who had recovered some .44 bullets that had been fired in his M29. He was astounded they actually measured .003 +/- under groove diameter......I don’t think he ever got a correct answer as to “why” as goodsteel and I were banned at the time so we couldn't tell him the reason his bullets were smaller than groove diameter after shooting..... ?

    BTW; Arizona gets lots of snow.......that big hole in the ground we have here called The Grand Canyon closes every winter because of.....you guessed it; snow. I-40 gets closed all the time in the winter due to snow. The southern part of the Rocky Mountains is in Arizona.....so there is lots of snow, especially at the large ski resort out of Flagstaff north of Phoenix. Arizona has 3,928 mountain peaks and summits…..more than any other Mountain State. Much of Arizona is above 7,000 fet…..including the Grand Canyon. Many times Arizona records the hottest temperature and coldest temperature in the Nation on the same day………Hell, It even snowed here in Lake Havasu City winter before last........

    Seriously, the test media Lars and goodsteel used (saw dust) deformed the bullets very little and they didn't have to wait until spring thaw to go find the bullets........ maybe and then being sure they were the “test” bullets shot some weeks or months before? Recovering bullets from test media is a proven method.....ever hear of forensic ballistic testing? Nobody conducting any serious bullet recovery, except some experts here, waits for the spring thaw......

    "there is a whole other train of [proven] thought about designing a pre-slumped bullet and then not launching it with a bunch of 4895."

    An absolute astute observation........note in the two HV examples above the use of the 30 XCB (NOE) bullet and the use of slow burning powders. A search may give up the RPM Threshold threads where I advocated this very early on (8+ years ago). I, Bjorn and a couple others have proven (by posting the data here on this forum numerous times that a properly designed bullet along with a proper slow burning powder (for the cartridge) is needed for HV cast bullet accuracy whether you have a slow twist to control the RPM or if you are pushing the RPM Threshold from a normal or fast twist barrel. Having partaken in the design of the 30 XCB, I know one of the primary design parameters was to mitigate "slumping" during acceleration as much as possible. That's why the XCB (NOE) has a minimal non bore riding nose, minimal size lube grooves and the maximum bearing surface for a "06/30-30 length case neck. However, I also have shown by extensive testing and posting the results on this forum even old classic cast bullets such as the 311041 or the 411466 can be driven to 2500 - 2600+ fps in 14 and 16" twist barrels with excellent accuracy in a cartridge of sufficient capacity that the slower burning powders can be used. The 311466 is also an excellent bullet to push the RPM Threshold with. Not quite as good as the 30 XCB (NOE) though.

    Controlling the RPM and keeping it below the RPM Threshold is the key to real HV cast bullet shooting. That fact has been proven by the posting actual test results over and over on this forum with excellent accuracy at 2600 to 3000 fps +/- demonstrated over and over again.

    Those who disagree that controlling the RPM isn't necessary with a naked, lubed, ternary alloy cast bullet at velocities of 2500 to 3000+/- fps should feel free to provide empirical test data here to show us how they can duplicate the mentioned accuracy/velocity out to at least 300 yards with the same ternary type cast bullets exceeding the RPM Threshold with 10 or 12" twist rifles. Those who disagree with the RPM Threshold all been offered that opportunity many, many times over several years now and none have provided any such alternative test data/results.

    The fact remains the reason the OP didn't hit the target with a cast bullet at 2900 fps was because his cast bullet load exceeded the RPM Threshold.

    Larry Gibson
    Last edited by Larry Gibson; 06-12-2017 at 12:16 PM.

  18. #18
    Boolit Grand Master OS OK's Avatar
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    Here we go again...you make a post and I learn something new...thanks for sticking with it.

    I've read about how the lube works many times trying to understand...it gets into the barrel through acceleration compression and centrifugal force slinging it out against the barrel and the cast then rides the film...but never have I'd imagined that our casts are riding an even film out and ahead of the cast blown out there by pressure.

    One would think that the front portion of the cast rides on dirty and fouled steel...never would I have imagined, that captured and measured casts are +/-.003" smaller.

    In extreme slow motion videos I've seen the flame come out of the crown ahead of the 'J-Type' projectiles...and, a substantial amount too...but my mind never took it to the level of what is actually happening around that 'cast' before it exits....never thought of the lube being distributed ahead of the cast...duuuh! I thought that was flame cutting...leading the bore.

    See...you post...I learn, thank you!
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  19. #19
    Boolit Grand Master Outpost75's Avatar
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    John Ardito set all of his CBA Heavy and Unlimited class group records firing 200-grain .308 bullets above 2200 fps from 14" twist barrels. Many of his records still stand long after the man has died.
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  20. #20
    Boolit Grand Master OS OK's Avatar
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    If my figures are near correct...that was at 113,142 RPM and on the low side of the thresholds...proving that point.
    I would imagine those casts were made with great care also...minimizing the interior flaws of a cast.

    Not sure if it has been stated but...BHN, I think is only one of the variables we control in casting/blending the boolit metal. The same BHN can be 'malleable or on the brittle side' depending on the contents.
    a m e r i c a n p r a v d a

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Abbreviations used in Reloading

BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
C Compressed Charge PR Primer SPCL Soft Point "Core-Lokt"
HP Hollow Point PSPCL Pointed Soft Point "Core Lokt" C.O.L. Cartridge Overall Length
PSP Pointed Soft Point Spz Spitzer Point SBT Spitzer Boat Tail
LRN Lead Round Nose LWC Lead Wad Cutter LSWC Lead Semi Wad Cutter
GC Gas Check