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September 22, 2010, 11:05 AM | #1 |
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Need some help customizing QuickLOAD
I've been using QL for several years and love it. But now I'm trying to develop loads for .38 S&W (a.k.a .38 Colt N.P.) and I'm having some problems; there's obviously something wrong in the cartridge database.
I have some actual Starline .38SW brass, and some .38 Special brass that's cut down to .775". The Special brass fits loose in the chambers because it's a slightly smaller diameter cartridge. So how come if I plug in the same powder, bullet, and length numbers in for .38 Special and .38 S&W, the .38SW comes up with a significantly higher pressure instead of slightly lower? I think the actual problem might be with the .38 Special data rather than the .38 S&W, because I've seen strange results when comparing .38 Special and .357 Magnum before. Also my .38 Special loads don't really match published load data very well; I put in their numbers and get much lower pressures and velocity. So, how do I measure the water capacity myself, assuming that's the measurement that's off? I have an idea: put 10 fired cases (so I get an average) on a digital scale and zero it, then fill each one to the top with distilled water with a drop of soap in it, and divide the weight by 10. Or is there another measurement that could be throwing things off?
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September 22, 2010, 11:38 AM | #2 |
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That's correct. Just be sure there is no meniscus, positive or negative. For rounds that fire below 30,000 psi do this with sized cases, and use fired case capacity for those running above that peak pressure. If you want, you can download the Excel file I made for water weighing from my file repository. It adds compensation for change in water density with temperature, but the difference is pretty small.
One problem with all brass is that SAAMI and the CIP only spec the outside dimensions of the brass. The internal case head dimensions and the the like are up to the manufacturer, so even though the QuickLOAD data shows suspiciously low case water capacity for the .38 S&W it could be correct for some make somewhere, and the program usually has a worst case default where the author knows what that is. Notice, for example, he has separate cases for .300 Win. Mag. for Winchester, Remington, Federal, and Norma because the cases are different enough to warrant that (and I suspect the author owns that chambering and has seen it).
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September 22, 2010, 11:44 AM | #3 | |
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Quote:
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September 22, 2010, 01:30 PM | #4 |
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Assuming you have correct dies for resizing .38 S&W, if your loads are too light to provide permanent expansion of the brass, just don't resize it. Decap, flare and seat and crimp. That's it. If you eventually find the bullet slipping into the case mouth, then apply the .38 S&W sizing die.
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September 23, 2010, 12:42 AM | #5 |
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My grandfather had an Iver Johnson 38 S&W breaktop 5 shot revolver in the Alaskan Gold Rush, and it is a family heirloom worth $50. But it interested me, so I bought a whole bunch of them at the guns show and overloaded them until I stretched the latch.
My father was chief engineer over 150 engineers and draftsmen for 40 years. He designed guns and vehicles. He is REALLY smart. I showed him an antique break top revolver I screwed up [Using ~ 38 Super +P type loading with jacketed 158 gr bullets] and said there was too much pressure. My father snapped at me, "That is not from pressure. That is from bullet friction and recoil acceleration on the some of the barrel mass." I did not get it. I had to think and think about what he said. After 2 days I could start to see it. So now when I shoot old 38 S&W break tops, I use wimpy loads with little recoil and soft lead bullets. |
September 23, 2010, 09:58 AM | #6 | |
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I'm trying to work up loads for a Colt Police Positive and a Webley top-break. Ultimately I want to give a box of ammo to a friend who has a S&W top-break. I'm starting with soft lead bullets for everything except maybe I'll use hard lead in the Colt and Webley (but not the S&W.) I'm not looking for a barn-burner load, just something accurate, not too filthy, and an honest 700 to 750 fps with a 150-ish grain bullet.
Since the Colt has a solid frame, j-bullets would probably be OK, but it was made in 1919 so I'm assuming the frame is soft steel and I don't want to abuse it. And I don't want to dust off my brain cells that have the "modulus of elasticity" stuff. Quote:
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September 23, 2010, 11:20 AM | #7 |
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There was a thread here a while back about the difficulty of running Quick Load for pistol and straight wall rifle cartridges. I think I would go with Lyman.
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September 23, 2010, 05:30 PM | #8 |
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QuickLOAD does do better with bottleneck rifle cases, but comes very close on a lot of the .45 ACP loads I use. If you have actual velocity data to work with, you can correct the errors.
Zxcvbob, To address your original question, no doubt, when the .38 Special Case and the .38 S&W case are given bullets seated to the same COL, it shows the .38 Special having a couple more grains of usable water capacity under the bullet. That may be part of the original case design? I don't know, but if you cut down .38 Special cases, there should be no difference in reality.
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September 23, 2010, 09:11 PM | #9 |
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Zxcvbob,
Looking at the calculations, I see several things: 1. The change in seating depth for the .38 Special to make it the same length as the .38 S&W does not make the remaining useable case capacities identical. The Special remains larger, for reasons that aren't clear. Further reducing the COL to match the Special available case capacity to the S&W case makes the Special pressure slightly higher than the S&W pressure. So, actually measuring your case capacities will be essential for making any more progress. 2. There are other differences, including the bore cross sectional area and the weighting factor. The weighting factor doesn't seem to make much difference (in this case) and the bore area difference makes much less difference than the case capacity. SL1 |
September 24, 2010, 07:47 AM | #10 |
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Zxcvbob,
One on other quick check you can do: if you have some actual commercial .38 S&W brass and some of your cut-to-same-length .38 Special cases, just weigh the two. If the .38 S&W brass actually has a couple of grains less water capacity due to thicker brass, it should weigh about 17 grains more at the same length.
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