7828 and the 378 Wby

KeithS · Apr 13, 2007

Okay, I loaded up 22 rounds of 300 grain CT Fail Safe moly coated bullets. Using my Nosler #3 guide and IMR 7828 powder, the recommended charge is 110 - 114 grains with the max load listed as the most accurate for their 300 grain Partition. I chose a middle of the road charge of 112.5 grains figuring that the moly probably would reduce pressure somewhat.

Midway had a sale on the Nosler #5 book so I picked it up. The load listed for the 300 grain patition and CT fail safe with 7828 is 107-111 grains and 100 fps slower all the way around. Now my quandry is my loads would be 1 1/2 grains over the #5 listed max, but still 1 1/2 grains under max load with the number 3 guide.

Should I pull the bullets and powder and start over, or shoot a few and watch for signs of pressure. I wonder why Nosler has reduced their charges. The number 3 guide was made in 1989. Has the IMR 7828 changed over the years, or is this just another conservative reduction in the wake of liability?

Good looking cartridge though!! :grin:

Guest · Apr 14, 2007

Not sure how many rounds you loaded up, but there is always the option of loading up some at the reduced load levels, and chronographing them to be sure you are getting what you think you're getting, and then working up to what you believe is a safe max charge for your rifle. If you find it before 112gr, then you pull the bullets. I, for one, would also get a blade mic and measure case-head expansion (use brass that has been fired once, measure and then fire and measure again) just to double check. I also would never load just one batch of loads and then call it a workup, unless I used the bottom start charge, and the exact components listed.

As for the change in charge weights, I think there are a couple of primary reasons. First, the way companies measure pressure data has changed since the late 1980's. Copper crusher measurements were not as reliable as the new peizoelectric transducer systems, which are more accurate, as well. So now we know more, especially about what pressures do at higher levels and how they behave based on max charge weights and such. I am no engineer, but one explained it to me that way, and I trust him. That said, I think the lawyers are also in the mix, but I am not so velocity hungry that I would play outside the lines much anyway. There just isn't enough to be gained to warrant overloading cartridges by much. Also, there may be some changes in 7828 over the years, you never know.

FOTIS · Apr 14, 2007

ACCORDING TO QUICKLOAD.......... BOLD ENTRY IS SAFE MAX

Cartridge : .378 Weath. Mag.
Bullet : .375, 300, NOS CT FailSafe 53360
Cartridge O.A.L. L6: 3.655 inch or 92.84 mm
Barrel Length : 24.0 inch or 609.6 mm
Powder : IMR 7828

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 85 90.00 2437 3956 37435 10946 93.6 1.498
-18.0 87 92.25 2498 4156 39991 11266 94.7 1.457
-16.0 89 94.50 2559 4362 42732 11569 95.7 1.417
-14.0 91 96.75 2620 4574 45677 11855 96.6 1.379
-12.0 94 99.00 2682 4790 48842 12122 97.5 1.341
-10.0 96 101.25 2743 5011 52246 12367 98.2 1.302
-08.0 98 103.50 2804 5238 55912 12589 98.8 1.262 ! Near Maximum !
-06.0 100 105.75 2865 5468 59866 12788 99.2 1.222 ! Near Maximum !
-04.0 102 108.00 2926 5703 64133 12960 99.6 1.184 !DANGEROUS LOAD-DO NOT USE!
-02.0 104 110.25 2987 5942 68742 13105 99.9 1.148 !DANGEROUS LOAD-DO NOT USE!
+00.0 106 112.50 3047 6185 73725 13222 100.0 1.112 !DANGEROUS LOAD-DO NOT USE!
+02.0 108 114.75 3107 6431 79141 13311 100.0 1.078 !DANGEROUS LOAD-DO NOT USE!
+04.0 111 117.00 3167 6680 84971 13390 100.0 1.045 !DANGEROUS LOAD-DO NOT USE!
+06.0 113 119.25 3226 6933 91276 13464 100.0 1.013 !DANGEROUS LOAD-DO NOT USE!
+08.0 115 121.50 3285 7189 98124 13531 100.0 0.982 !DANGEROUS LOAD-DO NOT USE!
+10.0 117 123.75 3344 7449 105576 13592 100.0 0.952 !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 106 112.50 3163 6667 88921 12660 100.0 1.033 !DANGEROUS LOAD-DO NOT USE!
Data for burning rate decreased by 10% relative to nominal value:
-Ba 106 112.50 2873 5499 59638 13364 96.7 1.217 ! Near Maximum !