Bronson7 Posted February 19, 2003 Share Posted February 19, 2003 Does anyone know of an equation that can be used to figure charge weights when oals are other than published. I'm asking this because my reloading data is showing a paricular charge of Universal at an oal of 1.275 for 45 ACP(230 rn), which is at maximum aol. I feel uncomfortable being at the maximum (or minimum) of anything and I'm wondering if there is a way to mathmaticaly interpolate or are there to many variables to do this? Thanks Bronson7 Link to comment Share on other sites More sharing options...
jmaass Posted February 19, 2003 Share Posted February 19, 2003 No. This would be caliber, powder, bullet, case, temperature, and air pressure related. VihtaVuori has published, in it's hardback reloading manuals, a formula for an increase in pressure and velocity based on delta-OAL for a sample of their powder in a particular caliber, etc. to demonstrate the danger of increased pressure with a small decrease of OAL. Link to comment Share on other sites More sharing options...
TBF Posted February 19, 2003 Share Posted February 19, 2003 I agree with Jeff, an example in Ramshot data book in 40 S&W shows almost double the pressure with only .010 shorter OAL. 45acp would most likely not be nearly as dramatic, but you are on the right track ask the question. What OAL are you contemplating ? I am sure someone may have some specific input if you are not attempting something very unusual. . Travis F. Link to comment Share on other sites More sharing options...
ryucasta Posted February 19, 2003 Share Posted February 19, 2003 Yes there is a way of calculating it by using products like Neconos Quickload Internal Ballistics Software. I have used this product for several years as my STARTING point when working up a load. Here's the link to the vendor and some generated numbers. http://www.neconos.com/details3.htm Cartridge : .45 Auto (ACP) (SAAMI) Bullet : .451, 230, SPR TMJ 4480 Cartridge O.A.L. L6 : 1.275 inch or 32.38 mm Barrel Length : 5.0 inch or 127.0 mm Powder : Hodgdon Universal Predicted data by increasing and decreasing the given charge, incremented in steps of 2.0% of nominal charge. CAUTION: Figures exceed maximum and minimum recommended loads ! Step Fill. Charge Vel. Energy Pmax Pmuz Prop.Burnt Btime % % Grains fps ft.lbs psi psi % ms -20.0 48 4.16 701 251 10330 2017 94.4 0.917 -18.0 49 4.26 716 261 10793 2074 95.1 0.898 -16.0 50 4.37 730 272 11269 2130 95.8 0.880 -14.0 51 4.47 744 283 11758 2185 96.3 0.863 -12.0 53 4.58 758 293 12260 2238 96.9 0.857 -10.0 54 4.68 772 304 12776 2291 97.4 0.840 -08.0 55 4.78 785 315 13305 2342 97.8 0.825 -06.0 56 4.89 799 326 13848 2393 98.2 0.809 -04.0 57 4.99 812 337 14406 2442 98.6 0.795 -02.0 59 5.10 825 348 14977 2489 98.9 0.781 +00.0 60 5.20 838 359 15563 2536 99.2 0.767 +02.0 61 5.30 851 370 16163 2581 99.4 0.754 +04.0 62 5.41 864 381 16778 2625 99.6 0.741 +06.0 63 5.51 877 392 17408 2667 99.7 0.729 +08.0 65 5.62 889 404 18052 2708 99.8 0.717 ! HOT LOAD ! +10.0 66 5.72 901 415 18712 2748 99.9 0.706 ! HOT LOAD ! Results caused by ± 10% powder lot-to-lot burning rate variation using nominal charge Data for burning rate increased by 10% relative to nominal value: +Ba 60 5.20 871 388 17992 2464 100.0 0.721 ! HOT LOAD ! Data for burning rate decreased by 10% relative to nominal value: -Ba 60 5.20 793 321 13183 2504 94.8 0.819 (Edited by ryucasta at 11:47 am on Feb. 19, 2003) Link to comment Share on other sites More sharing options...
DogmaDog Posted February 19, 2003 Share Posted February 19, 2003 You could figure out how case volume changes with seating depth. If you cut the volume in half, it should *theoretically* double the pressure, according to the ideal gas law (pv = nRt, pressure x volume = n (the amount of gas, in moles), R = a constant to get units to work, and t = absolute temperature. n should be directly proportional to charge weight (3 grains of powder produce half as much gas as 6 grains), and temp will be pretty much constant, unless it isn't. Of course, there may be very good reasons why this system would depart from the "ideal" in ideal gas law. It would be much safer just to reduce the loads, reduce OAL, and watch for pressure signs, and work up gradually. There isn't really any good reason to fear maximum OAL. Max OAL will produce the lowest pressure possible for a given powder charge. I think the Dillon instructions even say to load as close to max OAL as will reliably function in your gun. Anyway, all this has to do with peak pressure, and not with velocity. I don't think you'd see much effect on velocity at all by changing OAL. A pressure vs. time curve will get spikier (a higher, narrower peak) if you shorten OAL, but the area under the curve (=impulse) won't change much, so velocity won't change much. Finally, look in a different manual! My Laser Cast manual describes loads at 1.250" OAL for .45acp. (I don't have it at work, so I can't tell you what it says...I'll try to bring it tomorrow). You can consult Hodgdon's reloading manual online for free, though (although it only contains maximum loads) http://www.hodgdon.com Lata, DD Link to comment Share on other sites More sharing options...
Bronson7 Posted February 19, 2003 Author Share Posted February 19, 2003 Thanks guys. Was shootig for an aol of 1.260. I'll try the published 2.275 and see how it chambers. I thought there might be more to this than I thought. Bronson7 Link to comment Share on other sites More sharing options...
ryucasta Posted February 19, 2003 Share Posted February 19, 2003 Based on the new calculations in which the OAL was changed from 1.275 to 1.250 the maximum pressure increased by 1368 PSI for a like powder charge of 5.2 grains of Universal. Cartridge : .45 Auto (ACP) (SAAMI) Bullet : .451, 230, SPR TMJ 4480 Cartridge O.A.L. L6 : 1.250 inch or 31.75 mm Barrel Length : 5.0 inch or 127.0 mm Powder : Hodgdon Universal Predicted data by increasing and decreasing the given charge, incremented in steps of 2.0% of nominal charge. CAUTION: Figures exceed maximum and minimum recommended loads ! Step Fill. Charge Vel. Energy Pmax Pmuz Prop.Burnt Btime % % Grains fps ft.lbs psi psi % ms -20.0 52 4.16 716 261 11143 1998 95.0 0.901 -18.0 53 4.26 730 272 11652 2053 95.7 0.882 -16.0 54 4.37 745 283 12176 2107 96.3 0.864 -14.0 55 4.47 759 294 12715 2160 96.8 0.846 -12.0 57 4.58 773 305 13269 2211 97.3 0.830 -10.0 58 4.68 787 316 13839 2262 97.8 0.814 -08.0 59 4.78 801 328 14425 2311 98.2 0.799 -06.0 61 4.89 815 339 15027 2359 98.6 0.784 -04.0 62 4.99 828 350 15645 2406 98.9 0.769 -02.0 63 5.10 841 362 16279 2451 99.2 0.756 +00.0 64 5.20 855 373 16931 2496 99.4 0.742 +02.0 66 5.30 868 384 17599 2538 99.6 0.730 +04.0 67 5.41 881 396 18284 2579 99.8 0.717 ! HOT LOAD ! +06.0 68 5.51 893 408 18987 2619 99.9 0.705 ! HOT LOAD ! +08.0 70 5.62 906 419 19707 2657 100.0 0.694 ! HOT LOAD ! +10.0 71 5.72 918 431 20445 2693 100.0 0.683 !DANGEROUS LOAD-DO NOT USE! Results caused by ± 10% powder lot-to-lot burning rate variation using nominal charge Data for burning rate increased by 10% relative to nominal value: +Ba 64 5.20 887 402 19618 2414 100.0 0.698 ! HOT LOAD ! Data for burning rate decreased by 10% relative to nominal value: -Ba 64 5.20 810 335 14297 2479 95.4 0.794 Link to comment Share on other sites More sharing options...
DogmaDog Posted February 19, 2003 Share Posted February 19, 2003 ryacasta, Cool. Looks like your program predicts only 17 fps faster for the shorter load at a cost of 1368 psi in extra peak pressure. Yeah...that's what I'm sayin' DD Link to comment Share on other sites More sharing options...
DogmaDog Posted February 19, 2003 Share Posted February 19, 2003 Sorry for the drift, but, ryacasta, can you calibrate that Neconos software to your own chronograph data? That might almost approach being worth $150 DD Link to comment Share on other sites More sharing options...
ryucasta Posted February 19, 2003 Share Posted February 19, 2003 Dogma, The numbers have always come in +/- 6% (maximum). This in my opinion is no more of a difference than what you'll find between lots of the same brand of powder. This product has been very useful to me since it allows one to do what if scenarios. This particular feature has saved me countless hours when working up a load but then again YMMV. (Edited by ryucasta at 11:46 am on Feb. 19, 2003) Link to comment Share on other sites More sharing options...
TRG65 Posted February 19, 2003 Share Posted February 19, 2003 Dogma, I also use the Quick load software and once it is "calibrated" to the gun I've gotten a new load's calculated results to agree with test data to within 10 fps on pistol loads. I'm still on the learning curve with the program, I've only had it for about 2 months, but I recently found how to alter the temperature which has increased the agreement of my results. The only thing I haven't been able to find is a way to specify and change the primer types. I do like the feature that allows you to specify a pressure or velocity and the program tells you what charges of various powders can meet that velocity. Link to comment Share on other sites More sharing options...
Bronson7 Posted February 21, 2003 Author Share Posted February 21, 2003 Ryucasta, that's one hell of a program. I'm going to check it out. In the meantime I'll load to max oal to be on the safe side. Thanks gang. Great info. Bronson7 Link to comment Share on other sites More sharing options...
jrf Posted February 21, 2003 Share Posted February 21, 2003 Not sure what I'm missing, but those numbers don't seem to jive with what I've got for data for Universal and a 230grn plated bullet out of a 5" barrel?? Even Hodgdon's site has different numbers. At 6.0 grains of Universal with a 230grn plated bullet (very close to speer TMJ) loaded to 1.260 I'm getting 760 fps. That chart shows my load at almost 1000 fps? What am I missing? Link to comment Share on other sites More sharing options...
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