From: sfaber@ihlpb.att.com (Steven R Faber) Subject: Re: powder substitutions Organization: AT&T # In article <51819@mimsy.umd.edu>, cower@csli.stanford.edu (Richard Cower) writes: # | # | I'm trying to avoid buying a 1 lb of every powder made, and am wondering # | if anyone has some powder comparison chart? Specifically, I have an # | article by Layne Simpson that shows 82 gr. of IMR-3031, and 83 gr. of # | IMR-4064 - I don't have these. I do have IMR 4320, 4350 and 4381. Can # | I substitute these for the 3031 or the 4064 - and if so, in what # | quantities. The relative speed of the tubular IMR powders can be calculated based on the dimensions of the powder grains. This is outlined in the "Firearms Pressure Factors" book by Wolfe Publishing. The relative speed is inversely proportional to the amount of powder needed to produce a given pressure, all else equal. Here are some results from that book plus a comparison to data from the IMR reloading guide. q theo is the speed - the surface area to volume ratio for each powder normalized to 3031 as 1.00. q test is the value experimentally obtained by Brownell in the above book for a 30-06 (the value varied little with cartridge type as long as it was a shouldered cartridge). The following columns are speeds deduced by taking the ratios of the load weights between 3031 and the other powders given in the IMR guide for a 30-06 for each given bullet weight. All pressures were close to 50000 CUP. powd. q theo q test 110gr 150gr 180gr 200gr 230gr 4227 1.55 1.51 1.60 1.60 1.51 1.56 1.57 4198 1.13 1.18 1.42 1.30 1.24 1.24 1.29 3031 1.00 1.00 1.00 1.00 1.00 1.00 1.00 4064 .91 .93 .96 .95 .90 .94 .92 4895 .95 .94 1.03 1.00 1.02 1.03 1.05 4320 .96 .91 .97 .97 .91 .96 .97 4350 .75 .80 .84 .78 .81 .79 Note Brownell's experimental results track the theoretical within 5%. The IMR guide does not seem to correspond quite so well. The speed of 4198 seems to be about 10% higher with the IMR data and the speed of 4895 is around 8% slower than expected. The old Lyman manual I have seems to treat 4895 as a slower powder than 3031 - more like the Brownell results, I'll have to look into that some more. There seems to be in general a fair amount of variation between different reloading manuals. I think the Brownell data is good enough to go on and calculate starting charges for any of the above powders based on a known charge of another type. If you want to calculate pressure increases with load, he found that in the 50000 CUP region, the pressure varied as the 4th power of the load weight. So combine that with the q factor and you can calculate pressure for any load of any of the above powders once you have a known starting point -all other factors held constant. press = k * (q*Load)^4 Steve

From: sfaber@ihlpb.att.com (Steven R Faber) Subject: Re: powder substitutions - Lyman Organization: AT&T #From article <52264@mimsy.umd.edu>, by sfaber@ihlpb.att.com (Steven R Faber): # # The relative speed of the tubular IMR powders can be calculated # based on the dimensions of the powder grains. This is outlined # in the "Firearms Pressure Factors" book by Wolfe Publishing. # The relative speed is inversely proportional to the amount of # powder needed to produce a given pressure, all else equal. # Here are some results from that book plus a comparison to # data from the IMR reloading guide. # # q theo is the speed - the surface area to volume ratio for each powder # normalized to 3031 as 1.00. # q test is the value experimentally obtained by Brownell in the above # book for a 30-06 (the value varied little with cartridge type as long # as it was a shouldered cartridge). Here are the results summarized again with the Lyman data. The IMR results are the average of 5 bullet weights from 110 to 220gr shown before. The Lyman 30-06 are the averages from 10 bullet weights in the same range, and the .223 results are an average of 6 weights from 40gr to 63 gr. The Lyman 30-06 results gave pressures which varied somewhat so the results were adjusted for pressure: q = L3031/L*(P/P3031)^.25 The numbers in parens are the std deviations (error in the last one or 2 digits shown). powd. q theo q test IMR guide Lyman 30-06 Lyman .223 4227 1.55 1.51 1.62(8) 4198 1.13 1.18 1.30(7) 1.12(4) 3031 1.00 1.00 1.00 1.00 1.00 4064 .91 .93 .93(2) .943(13) .96(3) 4895 .95 .94 1.026(18) .972(10) .943(23) 4320 .96 .91 .956(26) .933(15) .912(22) 4350 .75 .80 .81(4) .833(15) 4831 .77 .777(19) # Note Brownell's experimental results track the theoretical # within 5%. (His data was taken from DuPont results). # The IMR guide has more variance and gives significantly higher speeds for 4198 and 4895 powders than the Lyman results, which match the theoretical and Brownell (DuPont) data better. Since the IMR results err towards higher speeds for those powders, the load weights would be more conservative. Steve

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