C.U.P.s/ P.S.I.=Lee Hardness tester?????

[Willyp]

I got a Lee tester and it gives harness values as to PSI! All or most,load data is in CUPs.
So,how does it correlate ????

[303Guy]

That would tensile strength of the alloy, not chamber pressure. I did see somewhere the correlation of tensile strength to chamber pressure but in psi. I'll see if I can find it again.

[geargnasher]

As far as I can tell, none of the formulas for "converting" CUP to PSI are worth a damn. What I do is refer to the Hodgdon online data and pick through it for PSI data if any is there, and/or reference Modern Reloading, 2nd edition because all the data is in PSI. Usually you can so a lot of comparing between loads and the PSI/CUP data for powders you can find and get a good idea what pressure your powder will make if you're using one that isn't listed in PSI anywhere.

Gear

[Willyp]

I guess my point is,Why didn't they print it in CPUs?????? I think i will call them and ask!!!!!!!

[geargnasher]

You mean why didn't Lee print it in CUPs? He explains that thoroughly in his book. He was trying to make it EASY us by keeping the alloy and chamber pressure measurements in the same, directly-transposable units. Chamber pressure data in PSI is directly measured with a strain gauge insead of a copper crusher, and is therefore more accurate and useful when comparing to the ultimate compressive strength of the alloy you use.

Gear

[303Guy]

The problem for me is that both psi values and CPU values are just a number. Neither have any real meaning to me. So for that reason I prefer to use the meaningless number labelled CPU as a reference or comparison. It's what I'm used to and until all CPU figures are gone, psi values serve only to confuse and quite simply, I ignore load date showing psi values and will do so until I know and understand the psi limits for each cartridge and gun.

There has to be some meaningful psi to CUP conversion. If not then we have to ignore CUP because it really is meaningless - but we know it's not (not entirely anyway). We do know it is highly inaccurate but it works.

[HangFireW8]

It is easy to convert... for the 45/70, where they are one in the same.

Unfortunately, US Ordnance, then US industry, continued using the same system for every new cartridge, without recalibrating it for each, or any. Once figures were published, the insanity was set in stone.

Of course, modern systems can better distinguish between peak pressure and sustained pressure... Not that a long sustained pressure is any safer for an old gun than a too-high peak pressure... so you see, the guys that came up with CUP for the 45/70 did a darned good job.

But back to your problem , what to do about CUP pressures and Lee's formula? The answer is, nothing. You see his formula has been disproven again and again, good results being obtained by violating his rule.

So don't sweat it. Concentrate on bullet fit and just use an alloy hardness level roughly suitable for the job at hand. For me it just means adding a little magnum shot to WW and water dropping for rifle, air dropping ww+tin and a little soft Pb for handgun, and soft Pb+tin for M/L and slow revolver loads, add some WW for faster loads.

HF

[runfiverun]

i'll save you a lot of math and worry.
forget about what richard lee says about the 90% thing.
keep your ww alloy pressures under 45k and things will be fine.

[Willyp]

Over a decade ago,i started to play with casting bullets. As i was just getting into it,i had to move to a new area for work,so,i quit.
All i cast was pure linotype,so i had no need to think about BHN and hardness of the lead and i was just learning? Linotype,i was getting for 10 cents a pound to mostly free! When i was about to move,i gave it to a guy whom took it to a scrap yard! How much i had,i don't know,but his Chevy truck sagged!!!!!!
My point is,now it cost quite a bit to buy it,so i figured i could just mix lead to get the minimum hardness for all around usage????? So,i bought the tester. It seems to be pretty close with the readings.
I checked some pure linotype,i had from years back and it came out about a 22,on the Lee chart?
All i want is to get a #2 mix of alloy!!!!!!!

[runfiverun]

cut the lino in half with soft lead and add 2% more tin.
that makes 4/6/90.
i use it for a few things.
if you just want ww like alloy cut the lino 1 part to 3 parts soft lead.
you can cut ww's with lino 3 to 1 and add 4% tin that will be right close to #2 also.

[Bret4207]

i'll save you a lot of math and worry.
Forget about what richard lee says about the 90% thing.
Keep your ww alloy pressures under 45k and things will be fine.

x100!!!

[MtGun44]

LOL!

+1 one the forget about it.

Bill

[Larry Gibson]

I guess my point is,Why didn't they print it in CPUs?????? I think i will call them and ask!!!!!!!

As runfive run mentions, ignore Lee's PSI to alloy use scale. It is not reliable. Sometimes it is correct and sometimes it is not. Sometimes it is close and sometimes it is way off.

There are other important variables that effect the accuracy potential of an alloy other than the simplistic way Lee compares the tensile strength of the alloys to the peak pressure a load may produce; actual composition of the alloy, rate of accelleration, velocity and RPM just to name a few. I can show you loads that shoot very well indeed at 38 - 44,000 psi with 18 -19 BHN alloys Lee says will fail at 26 - 27,000 psi. And yes, I actually measure the pressures, not guesstimate or correlate from manual data.

Larry Gibson

[mpmarty]

There is no way to correlate CUP to PSI reliably as copper crushers use a tare table to adjust for actual pressures measured in the crushed cylinder.

[HangFireW8]

As runfive run mentions, ignore Lee's PSI to alloy use scale. It is not reliable. Sometimes it is correct and sometimes it is not. Sometimes it is close and sometimes it is way off.


Yes, runfiverun mentioned that... in the post right after the one where I mentioned it.

[geargnasher]

I generally ignore Lee's 90% rule too, HOWEVER, I've tested his methods objectively many times and found them to work just fine, in fact it's the best way I can recommend to a new-ish cast boolit shooter a quick road to success. Good accuracy with minimal leading can be achieved in any caliber/cartridge I've tried using the simple guidelines layed out in his book. Now, does it mean much to me since I can and do routinely push alloys to three times their ultimate compressive strength with the same accuracy? Of course not. I know there are lots of other factors that bear on the accuracy/leading issue than simply looking at a guessed "peak" pressure and a crudely measured alloy strength value (one that pays no mind to composition of alloy, only to strength, and composition is probably even more important in reality), but the formula DOES work.

Gear

[Larry Gibson]

Yes, runfiverun mentioned that... in the post right after the one where I mentioned it.

My apologies HangfireW8, absolutely no intention to ignore or not give credit where credit is due. You did indeed say the same thing:drinks:

Larry Gibson

[mdi]

FWIW; I cast bullets for about 12 years before I got a hardness tester. When I sized my bullets to fit the gun, I got very little, or no leading with air cooled wheel weight alloy. I read all the posts about BHN vs chamber pressure vs tensil strength vs leading and couldn't completely figger it out (I have a grasp on the principles but all the trouble just wasn't worth it to me 'cause my loads didn't lead), so I went back to air cooled, properly sized wheel weight alloy (or equivalent) casting. For a while it was interesting/fun casting slugs and testing for hardness then marking the ingots, but I don't seem to have a need for that info. as long as my gun barrels remain lead free...

[MtGun44]

+1 on mdi

** get the fit right
** use aircooled wwts
** use a 'known good' design
** use a 'known good' lube

You'll have no problems 95%+ of the time.

Bill

[geargnasher]

You forgot one, Bill: Use a "known good" powder for the purpose and adjust the amount for best results. Sometimes powder choice alone can throw the whole shebang out of whack so badly that leading can happen even if everything else is right.

One more: Use a "known good GUN".

Gear

[Frank]

MtGun44:

+1 on mdi

** get the fit right
** use aircooled wwts
** use a 'known good' design
** use a 'known good' lube

You'll have no problems 95%+ of the time.

If air cooled ww's work fine your application, great. But maybe in another's application they may need a higher level of hardness. Remember, as pressure/velocity goes up, so do the requirements of hardness, lubrication and bore condition.

[Bret4207]

If that hardness rule was an actual rule then why is it that a 30 Bhn boolit isn't a guaranteed performer in all guns in all loads at, say, 2500 fps? There's a lot more to it than a Bhn reading or magic lube.

[0verkill]

If that hardness rule was an actual rule then why is it that a 30 Bhn boolit isn't a guaranteed performer in all guns in all loads at, say, 2500 fps? There's a lot more to it than a Bhn reading or magic lube.

Because Lee's theory says that pressure should be greater than the elastic limit but less than the compressive strength.
I agree that for the most part the theory works, but I wonder about what effect alloy composition has. Example lead with a lot of tin vs. lead with just a little antimony that has the same Brinell hardness number but could bevave differently from each other.
I also think that powder burn rate has a very large effect on accuracy with boolitsfrom my own observations. Which actually in Modern Reloading Richard talks about a 30-06 load with Red Dot and one with a rifle powder (forget which one) and that with recovered bullets the rifle powder load had better rifling engraving without stripping and more nose damage indicating higher impact velocity. I'd like to see more tests done with pressure testing equipment and actual velocities recorded along those lines.

[Larry Gibson]

like to see more tests done with pressure testing equipment and actual velocities recorded along those lines

I do that all the time. Just completed a test of CBA loads with 2131 recorded shots using reference ammuntion and VihtaVuori's Tin Star (N32C) powder in typical CBA cartridges. That's at the low end, at the high end I've been working with eddbadger with copper in the alloy pushing the 311466 bullets to 2680 fps and 44,000 psi. Lots of other tests in between. In the Lee test you mentioned while the peak psi was the same the time pressure curves were totally different. That was the difference. Same BHN for the bullet but one powder kicked in the butt and the other pushed it with TLC.

Larry Gibson

[MtGun44]

I can't disagree, gear - gun and powder definitely are key ingredients in the mix.

Bill

[mpmarty]

Not to worry, most new data is expressed in PSI as the copper crusher is on its way to obscurity (and good riddance). Most if not all current data is gathered from transducer measurements.

[303Guy]

I've been looking at piezoelectric pressures more lately since I've noticed some suspicious looking listed CUP values. I'm getting to not believing or trusting CUP values. I would love to see pressure traces - those would be more meaningful I would think.

[Bret4207]

Because Lee's theory says that pressure should be greater than the elastic limit but less than the compressive strength.
I agree that for the most part the theory works, but I wonder about what effect alloy composition has. Example lead with a lot of tin vs. lead with just a little antimony that has the same Brinell hardness number but could bevave differently from each other.
I also think that powder burn rate has a very large effect on accuracy with boolitsfrom my own observations. Which actually in Modern Reloading Richard talks about a 30-06 load with Red Dot and one with a rifle powder (forget which one) and that with recovered bullets the rifle powder load had better rifling engraving without stripping and more nose damage indicating higher impact velocity. I'd like to see more tests done with pressure testing equipment and actual velocities recorded along those lines.

Exactly. All the Bhn number tells you is relative hardness. It's just not that simple, same for Lees theory. The big problem is everyone is looking for the one easy answer and buy into theories like Bhn or Lees formula. Then when they have lousy results they are stumped. Been there, done that, got the tee shirt.

[0verkill]

I need to start keeping track of your posts. Any information on the effects of alloys?


like to see more tests done with pressure testing equipment and actual velocities recorded along those lines

I do that all the time. Just completed a test of CBA loads with 2131 recorded shots using reference ammuntion and VihtaVuori's Tin Star (N32C) powder in typical CBA cartridges. That's at the low end, at the high end I've been working with eddbadger with copper in the alloy pushing the 311466 bullets to 2680 fps and 44,000 psi. Lots of other tests in between. In the Lee test you mentioned while the peak psi was the same the time pressure curves were totally different. That was the difference. Same BHN for the bullet but one powder kicked in the butt and the other pushed it with TLC.

Larry Gibson

[44man]

As runfive run mentions, ignore Lee's PSI to alloy use scale. It is not reliable. Sometimes it is correct and sometimes it is not. Sometimes it is close and sometimes it is way off.

There are other important variables that effect the accuracy potential of an alloy other than the simplistic way Lee compares the tensile strength of the alloys to the peak pressure a load may produce; actual composition of the alloy, rate of accelleration, velocity and RPM just to name a few. I can show you loads that shoot very well indeed at 38 - 44,000 psi with 18 -19 BHN alloys Lee says will fail at 26 - 27,000 psi. And yes, I actually measure the pressures, not guesstimate or correlate from manual data.

Larry Gibson
I will not add to this. Larry really has a handle on this.
There is no way to compare cup to psi. Strain gauges give psi and cup is from compressed slugs. Do not mix them.

[Larry Gibson]

There is no direct correlation of CUP and piezo transducer psi measurments except in a vary narrow band and even that can be questionable. As mentioned don't try to correlate or you will go wrong.

Yes, different alloys can have an effect. Just recently I tested an alloy with copper in it against a 80/20 linotype/lead alloy using the 311466U bullet. Testing was done at high velocity in a .308W with a 14" twist palma barrel. Other than the bullet alloy all other componants were the same also. The velcocity for the identical load with each alloyed bullet was essentially the same, 2677 and 2678 fps, for both but the harder bullet with the copper alloy was at43,800 psi vs the ternary alloy at 38,700 psi. Internal ballistics for both were excellent with the SD and ES for both FPS and psi being essntially the same also.

Here are the 2 test data sheets.

Larry Gibson

[MtGun44]

Larry,
Thanks for the info. I tried to zoom in on the data sheets, could not
read them, othe rthan to see the general shape of the pressure pulses.
Interesting that the copper bearing alloy had 5,000 psi higher pressure.

What were the hardness numbers for the two alloys, and how did the accuracy
work out?

Bill

[Larry Gibson]

The ternary alloy is 80/20 linotype/lead and the AC'd bullets, after 10+ days aging have a BHN of 18-19. The copper alloyed bullets are WQ'd and have a BHN of 24-27 after the same 10 days. The ternary alloyed bullet load will hold 1.5 moa at 200 yards (10 shots) at 2600 fps. Above that the flyers creep in as the psi exceeds 40,000 and the bullet is exceeding the RPM threshold. The copper alloyed bullet is holding the same 1.5 moa at 2650 with 42,000 psi. At 2670+ fps and 43,000+ psi I get 1 -3 flyers out of the group.

I am maxed out at case capacity with the .308W. To get a higher velocity would require a faster powder and higher psi. That the opposite of what's needed. I'm thinking a 28-30" barrel with 16" twist chambered in '06 might be the next step. That would give the case capacity to use slower burning powders to keep the psi under 40,000 while allowing 2800+ fps.

However, before I do that there are a couple alloys with higher copper content to be tried. I want to work up to that Ideal alloy Lt. Whelen mentioned in his 1909 writings. If I can maintain 1.5 or better accuracy at 200 yards with 10 shot groups at 2670+ fps in the .308W Palma barrel with one of those copper alloys then I will step back to the .308W in 10 and 12" twists. I will then see how high a velocity that copper alloyed bullet can be pushed to and maintain the same 1.5 moa at 200 yards. I will then test it in the 30-06 with 10" twist barrel and slower powders to see where that goes.

That's the plan anyway but it will be delayed as it appears I've sold my house here in Washington. I will be moving to Lake Havasu City, Arizona area and buying a place there. So Im not sure when I will be set back up for extensive testing but I've told the wife all I want is a "man cave" that I can have a small indoor range in. I want set up my equipment in a lab atmosphere and at least be able to test the internal ballistics and velocity without hauling the equipment to a range and setting up to do it. There is a nice range there with 300 yards now to test accuracy on if I can't get a decent distance on my own place.

Larry Gibson

[badgeredd]

As Larry and Bret and others have said, I believe that hardness alone is obviously not the whole answer.

It is my experience up to this time that the copper in the babbit we are using toughens the alloy and makes it stronger. I'm hoping that through experimentation we can come up with alloys that will allow us to shoot milsurps at velocities comparable to the original loads with accuracy. If that can be done, then we'd be able to shoot cast boolit loads to the sights and in my book that would be HUGE! Beyond being able to shoot to the sights, I am thinking that this may work out to be a reasonable priced alternative to jacketed bullets, at least for target work. I realize that some are not the least bit interested in this goal, but I'm sure I am not alone in my quest.

Edd

[Larry Gibson]

A worthy goal Edd has. We shall continue to experiment toward that goal.

Larry Gibson

[GLL]

Larry kindly provided larger resolution images of his Data Sheets and gave me permission to repost them for all of us to examine.

Jerry

http://www.fototime.com/8BA96314E1E6E72/orig.jpg

http://www.fototime.com/D8A5AC8A50FB8EE/orig.jpg

[Larry Gibson]

If you notice the slight difference in the down range ballistics its because I corrected the BC on the Cu bullet to .230 based on actual measurement of that 311466U at 2600 fps. The .237 BC was measured at 2400 fps. If the down range screens are up in front of the target the M43 measures actual time of flight and the down range velocity. It can then compute the real BC. When actually measuring the down range velocities, TOF and BCs we can compare the BCs SD and ES and get an good handle on stability of the bullet; The higher the BC and the lower the SD and ES is the more stable the bullet. It makes interesting comparisons between different twist barrels with the same bullet at the same velocity. But, all that's a different story......

I've learned, having rebuilt several shot Skyscreens, that it's not wise to put the down range screens out until the loads accuracy and zero are proven. As many know, it really ruins your day shooting your screens. Not as bad as the whole chronograph though. That's the nice thing about the Oehler Skyscreens is parts are readily available and fairly inexpensive to rebuild them.

Thus I enter in the last measured BC or one from a known source. I can also change it to the type of BC it is; G1, etc.

None of that effects the "Inst" velocity reading at the muzzle screens or the psi measurements.

Larry Gibson