Lee's lated loading manual has a section that has the percent of pressure per .1 grain so that you can calculate what the max pressure would be to get the best load from your bullets.
Has anyone tried to calculate this formula? You need to know your bullet's hardness for it to work best so I ordered a Lee hardness tester today.
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I haven't seen the manual, but I'd be very cautious in using it to determine maximum loads. There's several variables that they can not possibly take into account as they would be unknown to Lee, such as actual case capacity (based on brand and lot), useable capacity (based on bullet seaing depth), jump to rifling (based on seating depth and rifle throating), primer brisance, actual bore and groove dimensions (rather than average published data). These will all affect pressure as much or more than bullet hardness.
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You need to read the Lee manual on what those numbers mean. It has nothing to do with calculation of pressure alone.
It was intended to be used to make reduced ladies and youth loads. The number following the load is how much velocity and pressure will go down per .1 gr of powder.
That manual also has other formulas for calculating cast bullet load and has many listing for cast bullet loads in several popular calibers.
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Exactly Jeff. I have no intention of using Max loads. I wanted to know about what pressure my light loads would produce. Too light and primers will pop out of the cases. As the manual states, many things change when you change your lead content and I wanted to know what would happen with the lead mixes I'm using.
I also ordered the LEE Harness Tester.
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AzShooter wrote:
Has anyone tried to calculate this formula? You need to know your bullet's hardness for it to work best so I ordered a Lee hardness tester today.
If this is the 2d edition, yes. I made a spreadsheet using two pressure and two velocity values from a Lyman 43d edition manual. If you have a start load and a max load, you can determine the reduction amount needed to reduce the max load pressure to the start load pressure. The book lists these in one grain increments, not .1 grain. The multiplier will change if using 1 grain increments, then changing to .1 grain increments.
If you are using a cartridge listed in the Lee Reloading book, then it is easier. Mine was not listed with the powder I was using, so I made the spreadsheet.
It looks like it comes close in the .308 win when trying to match the strength of linotype with the reduced load pressure.
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I have read the Lee 2nd Edition and like it very much. I did do some calculations as to pressure but since I like to shoot heat treated bullets it's really moot. Neat math though.~AMMOe
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Shooting heat treated bullets the BHC hardness will let you know how fast, or how much pressure they will take. If you heat treat you can load a lot hotter with the same bullet,almost like shooting J bullet velocities.
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I'm just now reading the Lee 2nd Edition book.. First I pick into it to see what it all had and looked over the numbers but have not put a pencil to them yet..
Enjoying it allot so far. I always find 1 or 2 new tricks with every book I read for re loading.
When you guys are done testing your lead,, send your $$$ tester to me to try,, RR Penokee, Ks.
Sodbust
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Paul, your post caught my eye about the 2nd ed. of LEE's Modern Reloading. I have tried to go through the data that the author presents on the 308 WIN w/150 gr, bullet as found on pg 426 and pgs. 122-128
He does not list a 1 grain factor for the H4895 powder and load, as presented
Were you able to come up with a means and/or method to calculate that 1 grain factor when you developed your speadsheet? And how did he modify to solve for an actual 1/2 grain reduction with % reduction averages based on 1 % reductions in charge?
As you may have noticed I'm quite interested in cast bullets and reloading and Mr. Lees' innovations, But I must have missed something in his text, can you help?
Thanks, James.
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Since your load is not listed in the Lee manual, I went to the Hodgdon 2007 Annual Manual. There is a 150 gr load listed with H4895. There is a start load with velocity and pressure; there is a maximum load with velocity and pressure.
Start Load: 43.0 gr H4895, 2742 fps, 43,200 CUP.
Maximum Load: 45.5 gr H4895, 2870 fps, 51,000 CUP.
Since the start load is 43 and the max is 45.5, try .5 grain increments in your spreadsheet. Your velocity factor is multiplied by the max velocity and you need it to agree with 43.0 grain load.
This is too confusing. I'll try to send an excel spreadsheet attachment.
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Thanks, Paul. I was able to up load the spreadsheet and see how you calculated the data.
Yes it is confusing. That velocity and pressure factor, I take it, must be derived from the difference between the max and the min values divided by the size of the steps you want.
MAX velocity 2870 fps - MIN velocity 2741 fps = 129
45.5 gr. - (0.5 gr x 5) = 43 gr. so 129 / 5 = 25.8 and 2870 - 25.8 = 2844.2 fps
2870 x Vfactor = 2844.2 so 2844.2 / 2870 = .9910104
or as close as practical but as you pointed out the values must agree with the 43 gr values or the starting load values, so the last increment step times the Vfactor equals 2741 fps at 43 gr. load.
And then do it all again for the Pfactor! A Kind of back and forth motion between picking a factor value then checking it then changing the factor and rechecking to get as close as posible to the starting load values given.
And the spreadsheet HELPS tremendously with the calculations! Thanks again. I think I should be able to check the authors 1 grain factor values now against what I can calculate and what I see in his reloading handbook,
James S
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Read all the caveats Mr Lee has included in his book, and then you can do the arithmetic. Above all this is used for calculating REDUCED loads, for a case and powder where you have all the data. Also remember that some powders (slow ones mostly), will ring a chamber, and there goes your cost saving.
Also note that this is done to match his findings that best accuracy comes with a load that is 90% of the tensile strength of the lead.
OK the arithmetic. Of necessity you have to have a load with the same weight of bullet, for which you have starting and max pressure readings.
For simplicity lets say there are 5 grains of powder between the two. To calculate your reduced pressure, grain by grain, you multiply the starting pressure repetitively with the bugger factor.That means that max pressure x BF^5 is starting pressure. Obviously then the BF is the 5th root of the ratio of Starting pressure to Max pressure.
So if you have a load that has 3.7 gr between the two pressures you take the 1/3.7th root( I don't know how to do that either, but your calculator does. Get your kids to show you how, that's what I do.) and that's your BF. The same reasoning applies to velocity, but since we're trying these out to find the most accurate load, who cares how fast it's going
... certain dangerous habits of thought. One is that, while all important enterprises need careful organization, it is the organization that needs organizing, rather than the enterprise. And another is that tranquility is always a good thing. - Terry Pratchett
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I am reading this book currently. I found Mr Lee's comment on page 157 regarding the safe reduction of charges for slow burning powders to be interesting. I also found it interesting that his cast loads pages 140 to 155 employ several relatively slow burning powders not commonly seen in the FS.
Is he breaking new gound or trying to make a point? Anyhow it is interesting reading.
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Breaking new ground? Nope, lots of surplus 4831, BallC2 and 4895 was burned with cast bullets in the '70's. Making a point? Maybe. The main problem for me is that mid to slow powders, especially ball ones, are terribly inaccurate after three or four shots. There is so much residue in the bore, you never have the same conditions. If you are happy with 2 1/2” groups, go right ahead. But a lot of us have been down this road, and don't want to head there again.
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