7 PRC and US869

[waldedw]

I have a swack of US869 that I used in my 7 RUM which I don't have anymore, anyway I have been trying to find some load data for US869 and the 7 PRC to no avail. I have a load for my 6.5 PRC with US869 and the 142gr NABLR which are now as hard to find as RL26 I think they are ferry dust. That load is very accurate however it's about 75 FPS slower than the load with RL25.

I see US869 is about 4 notches slower on the burn rate chart than LRT, there is load data available for LRT for the 7 PRC with 175gr and any data I find for any cartridge that shows both LRT and US869 in every case the max charge of US 869 is the same or 1 gr more. Keeping with that LRT shows a max 80gr with the 175gr in 7 PRC and I was thinking I am going to load some test loads with US869 starting around 74gr and working up 1/2 gr at a time until I start to see pressure.

I measured an empty case for the 7 PRC and filled to the base of the neck I can get 83gr US869 in it so should be able to load near max loads without to much compression.

I've been loaded for 50 years now but have always used published data as a starting point and going from there, am I on the right track here fellows or am I peeing into the wind, seeing that Alliant has suspended powder manufacture for a while anything RL is going to become more scarce than it already is, I have a couple loads that show promise for the 7 PRC with RL25 and H1000

[Dean2]

I would call Hodgdon and ask them if they have a starting load for US869 and the 7PRC. They have always been amazingly helpful when I have called them.

[waldedw]

Originally Posted by Dean2

I would call Hodgdon and ask them if they have a starting load for US869 and the 7PRC. They have always been amazingly helpful when I have called them.

Thanks Dean I went that route already, they said they have not tested US896 in the 7 PRC as of yet

[Dean2]

Well, in that case, I would take the start load for a 6.5 PRC with the same bullet weight and start there and work my way up. The good thing about 869 is it is so damn SLOOOOWWWW, it has a burn rate similar to wet coal, it would be hard to get very far over pressure in the 7 PRC cartridge. Even in the 7 RUM there is barely enough capacity to get high pressure.

[brewster29]

I was able to find QL data for US869 in a 7 REM mag…
Given that the 7 PRC case is pretty much the same volume it might be worth a try, although velocities are low. My 7PRC like LRT and Retumbo with 175’s.

Cartridge : 7 mm Rem. Mag.(SAAMI)
Bullet : .284, 195, Berger ElHunt G7 #28550
Useable Case Capaci: 68.686 grain H2O = 4.460 cm³
Cartridge O.A.L. L6: 3.290 inch = 83.57 mm
Barrel Length : 26.0 inch = 660.4 mm
Powder : Hodgdon US 869

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 90 60.72 2143 1989 28334 9127 79.3 1.905
-18.0 92 62.23 2206 2107 30474 9500 81.1 1.848
-16.0 95 63.75 2270 2231 32797 9870 82.8 1.794
-14.0 97 65.27 2334 2360 35324 10233 84.5 1.741
-12.0 99 66.79 2400 2494 38076 10589 86.1 1.686
-10.0 101 68.31 2466 2634 41081 10935 87.7 1.626
-08.0 104 69.82 2533 2779 44367 11270 89.1 1.568
-06.0 106 71.34 2601 2930 47967 11591 90.6 1.511
-04.0 108 72.86 2670 3087 51919 11897 91.9 1.456 ! Near Maximum !
-02.0 110 74.38 2740 3250 56270 12185 93.2 1.404 ! Near Maximum !
+00.0 113 75.90 2810 3419 61071 12454 94.3 1.352 !DANGEROUS LOAD-DO NOT USE!
+02.0 115 77.41 2881 3594 66387 12700 95.4 1.303 !DANGEROUS LOAD-DO NOT USE!

[waldedw]

Well yesterday I loaded up a batch of test loads with 175 gr ELDX and US869, LRT and US869 have the same burn rate, data showed LRT max charge was 80gr with a 180gr berger so I felt confident that using LRT data with US869 and 175gr bullets.

No signs of pressure all the way up to 80gr, primers not even flat so probably could go to 81 or 82 without a problem.

Hornady 175gr ELDX precision hunter factory loads average 2958 fps out of my gun and I was hoping to get up to that velocity but was skeptical given US869 is so slow, but as you see below I got to 2960, now to load some at 80gr and see how they shoot and collect the data from the Garmin Xero C1 for more accurate average velocity, ES and SD and hopefully shoot some good groups.

Below is the velocity of I guess what would be a ladder test, never did one before.

72gr - 2522 fps
73gr - 2590 fps
74gr - 2673 fps
75gr - 2695 fps
75.5gr - 2729 fps
76gr - 2755 fps
76.5gr - 2808 fps
77gr - 2847 fps
77.5gr - 2851 fps
78gr - 2852 fps
78.5gr - 2885 fps
79gr - 2902 fps
79.5gr - 2905 fps
80gr 2960 fps