POP-Help need-270WbyMag
- Thread starter CZ
- Start date
- Thread starter
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REDGREEN
Handloader
- Mar 30, 2006
- 276
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Max load of IMR 7828 is 72.0 grains @ 3215 fps. Chamber pressure is 53600 CUP.
G
Guest
Guest
Well, Hornady used Weatherby cases for their testing, and Fed215 primers, but here's the listing from two different manuals:
From Hornady #4
150gr bullet
IMR7828 73.3gr 3000fps range from a 24" barrel
From Hornady #7
150gr bullet
IMR7828 67.8gr 3000fps range from a 26" barrel
I'm finding it interesting to compare the data from #7 (most recent) with #4 (fifth printing 1996), as many of the magnums are significantly lower in powder charge from then to now. I notice velocities are similar in many cases, and it's only from careful observation that I discovered that Hornady's new test barrels are all noticeably longer than their old test barrels! I have worked up from IMR's most recent published data for my 270Wby to their published max charge of 76gr, but that is for a 130gr, not a 150gr. I'm getting exactly the velocities they published, so I am confident I'm not doing anything freaky. Hornady's data is well below what the powder manufacturers are publishing in many instances now, also. I'd suggest using the IMR data, working up in small increments from about 5% below max, and watching carefully for any variations in velocity from what IMR got, as well as case stretch, primer flattening/cratering, and if you have a blade mic, case head expansion (but only use once fired brass for that).
The standard I use for the 270Wby is that the 150gr bullet can be driven by the right powders to a velocity in the 3100-3200fps range, or perhaps just over 3200fps. If you're getting much more than 3200fps out of a 150, I'd say you've exceeded safe limits by a wide margin.
From Hornady #4
150gr bullet
IMR7828 73.3gr 3000fps range from a 24" barrel
From Hornady #7
150gr bullet
IMR7828 67.8gr 3000fps range from a 26" barrel
I'm finding it interesting to compare the data from #7 (most recent) with #4 (fifth printing 1996), as many of the magnums are significantly lower in powder charge from then to now. I notice velocities are similar in many cases, and it's only from careful observation that I discovered that Hornady's new test barrels are all noticeably longer than their old test barrels! I have worked up from IMR's most recent published data for my 270Wby to their published max charge of 76gr, but that is for a 130gr, not a 150gr. I'm getting exactly the velocities they published, so I am confident I'm not doing anything freaky. Hornady's data is well below what the powder manufacturers are publishing in many instances now, also. I'd suggest using the IMR data, working up in small increments from about 5% below max, and watching carefully for any variations in velocity from what IMR got, as well as case stretch, primer flattening/cratering, and if you have a blade mic, case head expansion (but only use once fired brass for that).
The standard I use for the 270Wby is that the 150gr bullet can be driven by the right powders to a velocity in the 3100-3200fps range, or perhaps just over 3200fps. If you're getting much more than 3200fps out of a 150, I'd say you've exceeded safe limits by a wide margin.
- Oct 30, 2004
- 24,394
- 3,321
Cartridge : .270 Weath. Mag.
Bullet : .277, 150, Hornady SP 2740
Cartridge O.A.L. L6: 3.295 inch or 83.69 mm
Barrel Length : 26.0 inch or 660.4 mm
Powder : IMR 7828 SSC
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 B_Time
% % Grains fps ft.lbs psi psi % ms
-20.0 77 54.40 2549 2164 32315 10570 92.0 1.636
-18.0 79 55.76 2613 2275 34530 10900 93.3 1.593
-16.0 81 57.12 2678 2389 36898 11215 94.5 1.551
-14.0 83 58.48 2743 2506 39430 11514 95.5 1.503
-12.0 85 59.84 2808 2626 42136 11795 96.5 1.456
-10.0 86 61.20 2872 2748 45040 12056 97.3 1.411
-08.0 88 62.56 2937 2873 48150 12297 98.1 1.368
-06.0 90 63.92 3001 2999 51484 12516 98.7 1.326
-04.0 92 65.28 3065 3128 55060 12710 99.2 1.286 ! Near Maximum !
-02.0 94 66.64 3128 3259 58901 12880 99.6 1.247 ! Near Maximum !
+00.0 96 68.00 3191 3392 63031 13024 99.8 1.209 ! Near Maximum !
+02.0 98 69.36 3254 3527 67450 13140 100.0 1.174 !DANGEROUS LOAD-DO NOT USE!
+04.0 100 70.72 3316 3662 72173 13230 100.0 1.139 !DANGEROUS LOAD-DO NOT USE!
+06.0 102 72.08 3377 3799 77243 13310 100.0 1.105 !DANGEROUS LOAD-DO NOT USE!
+08.0 104 73.44 3438 3938 82692 13386 100.0 1.073 !DANGEROUS LOAD-DO NOT USE!
+10.0 106 74.80 3499 4077 88557 13457 100.0 1.042 !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 96 68.00 3324 3680 76141 12504 100.0 1.119 !DANGEROUS LOAD-DO NOT USE!
Data for burning rate decreased by 10% relative to nominal value:
-Ba 96 68.00 2997 2992 50777 12985 95.7 1.328
Cartridge : .270 Weath. Mag.
Bullet : .277, 150, Hornady SP 2740
Cartridge O.A.L. L6: 3.295 inch or 83.69 mm
Barrel Length : 26.0 inch or 660.4 mm
Powder : Alliant Reloder-25
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 B_Time
% % Grains fps ft.lbs psi psi % ms
-20.0 82 56.00 2553 2171 31241 10734 97.4 1.666
-18.0 84 57.40 2617 2281 33402 11000 98.3 1.622
-16.0 86 58.80 2680 2393 35718 11241 99.0 1.580
-14.0 88 60.20 2743 2507 38198 11455 99.5 1.534
-12.0 90 61.60 2806 2622 40853 11639 99.8 1.485
-10.0 92 63.00 2868 2739 43707 11793 100.0 1.439
-08.0 94 64.40 2929 2857 46765 11919 100.0 1.395
-06.0 96 65.80 2989 2976 50050 12038 100.0 1.352
-04.0 98 67.20 3049 3096 53582 12154 100.0 1.311
-02.0 100 68.60 3108 3217 57377 12267 100.0 1.271 ! Near Maximum !
+00.0 102 70.00 3166 3339 61463 12376 100.0 1.233 ! Near Maximum !
+02.0 104 71.40 3224 3463 65860 12480 100.0 1.196 !DANGEROUS LOAD-DO NOT USE!
+04.0 106 72.80 3282 3587 70551 12581 100.0 1.161 !DANGEROUS LOAD-DO NOT USE!
+06.0 108 74.20 3339 3713 75581 12678 100.0 1.127 !DANGEROUS LOAD-DO NOT USE!
+08.0 110 75.60 3396 3840 80980 12770 100.0 1.094 !DANGEROUS LOAD-DO NOT USE!
+10.0 112 77.00 3452 3969 86784 12858 100.0 1.063 !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 102 70.00 3279 3581 75370 11948 100.0 1.139 !DANGEROUS LOAD-DO NOT USE!
Data for burning rate decreased by 10% relative to nominal value:
-Ba 102 70.00 2993 2983 48760 12919 99.5 1.359
Bullet : .277, 150, Hornady SP 2740
Cartridge O.A.L. L6: 3.295 inch or 83.69 mm
Barrel Length : 26.0 inch or 660.4 mm
Powder : IMR 7828 SSC
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 B_Time
% % Grains fps ft.lbs psi psi % ms
-20.0 77 54.40 2549 2164 32315 10570 92.0 1.636
-18.0 79 55.76 2613 2275 34530 10900 93.3 1.593
-16.0 81 57.12 2678 2389 36898 11215 94.5 1.551
-14.0 83 58.48 2743 2506 39430 11514 95.5 1.503
-12.0 85 59.84 2808 2626 42136 11795 96.5 1.456
-10.0 86 61.20 2872 2748 45040 12056 97.3 1.411
-08.0 88 62.56 2937 2873 48150 12297 98.1 1.368
-06.0 90 63.92 3001 2999 51484 12516 98.7 1.326
-04.0 92 65.28 3065 3128 55060 12710 99.2 1.286 ! Near Maximum !
-02.0 94 66.64 3128 3259 58901 12880 99.6 1.247 ! Near Maximum !
+00.0 96 68.00 3191 3392 63031 13024 99.8 1.209 ! Near Maximum !
+02.0 98 69.36 3254 3527 67450 13140 100.0 1.174 !DANGEROUS LOAD-DO NOT USE!
+04.0 100 70.72 3316 3662 72173 13230 100.0 1.139 !DANGEROUS LOAD-DO NOT USE!
+06.0 102 72.08 3377 3799 77243 13310 100.0 1.105 !DANGEROUS LOAD-DO NOT USE!
+08.0 104 73.44 3438 3938 82692 13386 100.0 1.073 !DANGEROUS LOAD-DO NOT USE!
+10.0 106 74.80 3499 4077 88557 13457 100.0 1.042 !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 96 68.00 3324 3680 76141 12504 100.0 1.119 !DANGEROUS LOAD-DO NOT USE!
Data for burning rate decreased by 10% relative to nominal value:
-Ba 96 68.00 2997 2992 50777 12985 95.7 1.328
Cartridge : .270 Weath. Mag.
Bullet : .277, 150, Hornady SP 2740
Cartridge O.A.L. L6: 3.295 inch or 83.69 mm
Barrel Length : 26.0 inch or 660.4 mm
Powder : Alliant Reloder-25
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 B_Time
% % Grains fps ft.lbs psi psi % ms
-20.0 82 56.00 2553 2171 31241 10734 97.4 1.666
-18.0 84 57.40 2617 2281 33402 11000 98.3 1.622
-16.0 86 58.80 2680 2393 35718 11241 99.0 1.580
-14.0 88 60.20 2743 2507 38198 11455 99.5 1.534
-12.0 90 61.60 2806 2622 40853 11639 99.8 1.485
-10.0 92 63.00 2868 2739 43707 11793 100.0 1.439
-08.0 94 64.40 2929 2857 46765 11919 100.0 1.395
-06.0 96 65.80 2989 2976 50050 12038 100.0 1.352
-04.0 98 67.20 3049 3096 53582 12154 100.0 1.311
-02.0 100 68.60 3108 3217 57377 12267 100.0 1.271 ! Near Maximum !
+00.0 102 70.00 3166 3339 61463 12376 100.0 1.233 ! Near Maximum !
+02.0 104 71.40 3224 3463 65860 12480 100.0 1.196 !DANGEROUS LOAD-DO NOT USE!
+04.0 106 72.80 3282 3587 70551 12581 100.0 1.161 !DANGEROUS LOAD-DO NOT USE!
+06.0 108 74.20 3339 3713 75581 12678 100.0 1.127 !DANGEROUS LOAD-DO NOT USE!
+08.0 110 75.60 3396 3840 80980 12770 100.0 1.094 !DANGEROUS LOAD-DO NOT USE!
+10.0 112 77.00 3452 3969 86784 12858 100.0 1.063 !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 102 70.00 3279 3581 75370 11948 100.0 1.139 !DANGEROUS LOAD-DO NOT USE!
Data for burning rate decreased by 10% relative to nominal value:
-Ba 102 70.00 2993 2983 48760 12919 99.5 1.359
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