9.3x62 vs. 375 Whelen Improved

There is precious little data out there for 375 whelen improved, so I’ve always struggled with loads for mine. I just put together a 9.3 x 62 on an M1917 action. There is tons of data for the 9.3x62 so I got to thinking, the cases look like they’d have similar capacities.

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After I get some 9.3 brass fireformed, I’m going to take about 10 cases from both calibers and test them for volume. If they are close, using 9.3 starting data may be a good starting place for different loads in the 375 Whelen. Ive got my fingers crossed.


JTD

On the left is one of my fireforming rounds for 375 whelen AI, with Speer 235gr ssp and IMR4064. On the right the 9.3x62 with new brass, and 270gr Speer sp with RL15. I hope I can make it to the range tomorrow.

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JTD

Pre and post 375 whelen AI.

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JTD

How close to 375 H&H are you coming with that ?? --- SAWMAN

I’m still playing with it. All I’ve shot out of it so far is the 235gr Speer. It does not shoot them well. Ive got 2 boxes of 270gr Speer bullets to try, when I’m done fire forming the last of my brass. I don’t think it is going to get very close to H&H performance, my best load with the 235gr was just under 2600fps, but was not a max load. I will update as I go.


JTD

STILL . . . will be a great killer.
The vels that you end up with might be more compatable with your choice of bullets. The heavier bullets will still give you the momentum but there should be more penetration. If you hit bone going in that would be better.
Then you have "hole size". The bigger,the better. Even at 150fps below a 375H&H it will still quite effectively kill anything you will hunt. Even the bigger bear.
There are also some bullet choices that ARE NOT designed to be used in the 375H&H that could be a better choice,depending on the game animal.
Good luck with this project sir. ---- SAWMAN

Thanks SAWMAN.


JTD

From the best I can figure, I will be getting 200-300fps less velocity than the 375H&H. That should still give me enough velocity for adequate terminal performance inside of 200 yds. Once I get a chance to do proper load development I will know more.


JTD

So I’ve now got fire formed brass for both rifles.

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I took five pieces of brass for each and figured out the volume, and just as I expected, they were very close. I took the weight of each case empty and the weight of each case with rubbing alcohol in them, and took the difference to figure volume.

9.3 brass -
Empty. Full. Vol.
202.3. 267.7. 65.4
201.8. 267.6. 65.8
200.8. 266.7. 65.9
201.5. 267.1. 65.6
205.6. 270.6. 65.0
Avg. 65.54
375 brass -
200.5. 265.0. 64.5
200.1. 264.7. 64.6
198.8. 263.6. 64.8
199.5. 264.4. 64.9
198.8. 263.5. 64.7
Avg. 64.7

Only a difference of .84, so that means I should be able to use starting loads for the 9.3x62 for my starting loads for the 375whelen AI. I love it when a plan comes together.


JTD

So since my volume test I’ve loaded the 9.3x62 up to 58.5gr of RL15 with 270gr bullets. Primers started to flatten with this load. Ive loaded the 375 Whelen Improved up to 58.0gr of RL15 and a 270gr bullet with no pressure signs. I’m going to shoot 58.5gr this weekend. I think my theory was correct, that I could use 9.3x62 load data for the 375 Whelen Improved.


JTD