Extrapolating data for the .375 Chatfield-Taylor from .338 Win Mag?

CoryTheCowboy

CoryTheCowboy

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Howdy folks,

I currently have a .375 Chatfield-Taylor on it's way to me, and have done a fair bit of research on appropriate powders (seems Varget, 4064, RL15 are favoured). I have D4895 which I think is a little bit faster than them, but hope will work. The only other powder I have any real supply of is H4831. I have both 300gr and 235gr bullets coming, and am hoping to come up with a 235gr load to carry while deer and bear hunting this fall.

Since it's just a necked up .338 Win Mag, I was wondering about using .338 data with the same bullet weight as a starting point? I'm assuming (which I don't really like doing with reloading) that since I'll have a bigger bore, I'd have lower pressure? Then work up with the Chrony watching velocity and for pressure signs. I'm mostly just wondering if I'm on the right track.

Thank you,

Cory
 
Probably not much help to you, but posted on Accurate Forum in July 2021: "FWIW, the latest version of QuickLoad includes the .375/338 Chatfield-Taylor." So, if you have that, or can find someone who does have that, I understand that program may help you to come up with something to start with?? As per other Internet postings, is apparently a number of nearly identical cartridges - for example, 375 Newton - that might produce loading information, searching under those other names? Is all perhaps not news to you?

Is something that I never tried - start from cold, and not having a plethora of powders on hand to try - but even so, sort of need a place to start from - no?

Some years ago, was at least one article by John Barsness - is reproduced as a chapter in one of his books, here - about "ballistic rules" - was about using loading data for one cartridge - say 130 grain 270 Win, and manipulating it with math to come up with expected results for a 250 grain 338 Win Mag (or something like that) - but I do not recall anything about using that to establish a suitable powder - was about what would be the expected velocity, etc., with equivalent pressure - with "suitable" powders - as I recall.

Pierre Van Der Walt described a technique to measure velocity as one increased powder loads incrementally - was the velocity gain per grain weight of powder that you were concerned about - when that rate of increase changed, was telling you something about that load - I would have to re-read that - has been a few years - but I think that guy was writing a lot about the "bigger boomers" as used in Africa.
 
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CoryTheCowboy said:
Howdy folks,

I currently have a .375 Chatfield-Taylor on it's way to me, and have done a fair bit of research on appropriate powders (seems Varget, 4064, RL15 are favoured). I have D4895 which I think is a little bit faster than them, but hope will work. The only other powder I have any real supply of is H4831. I have both 300gr and 235gr bullets coming, and am hoping to come up with a 235gr load to carry while deer and bear hunting this fall.

Since it's just a necked up .338 Win Mag, I was wondering about using .338 data with the same bullet weight as a starting point? I'm assuming (which I don't really like doing with reloading) that since I'll have a bigger bore, I'd have lower pressure? Then work up with the Chrony watching velocity and for pressure signs. I'm mostly just wondering if I'm on the right track.

Thank you,

Cory
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That works pretty well, due to the larger bore size. You shouldn't have any issues, just be careful with the heavier bullets taking up case volume. - dan
 
dan belisle said:
That works pretty well, due to the larger bore size. You shouldn't have any issues, just be careful with the heavier bullets taking up case volume. - dan

CORYTHECOWBOY said:
Since it's just a necked up .338 Win Mag, I was wondering about using .338 data with the same bullet weight as a starting point? I'm assuming (which I don't really like doing with reloading) that since I'll have a bigger bore, I'd have lower pressure? Then work up with the Chrony watching velocity and for pressure signs. I'm mostly just wondering if I'm on the right track.
Click to expand...
Click to expand...

Good plan, Cory, and the best encouragement so far, Dan.

The expansion ratio is considerably higher with the 375 bore, so any safe 338 loads will be safe in the 375CT using the same bullet weight and powder charge.

Ted
 
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I ended up extrapolating data for my 35-338 a few years ago from other cartridges of the same bore dia, same bullet weights and similar capacity cases mostly 358 Norma & worked up slowly with a chronograph & watching for any signs of excess pressure.
The loads I ended up settling on as what I consider max for my rifle would be roughly 95-96% of book max charge weights for 358 Norma.
375 CT with the same weight bullets and same powder will be less pressure than 338 & 35-338.
Using 338 win mag data would be very safe imo due to all the extra volume in the bore for expansion of gases in a 375.
I think most people loading for 375 CT would be loading alot closer to 358 Norma max published data than 338 Win data.
Good luck with working up yer loads, not much that thing won't kill quickly.
 
I found 375/338 Chatfield Taylor on Quickload. I can run some loads on QL for you, will need this info
- powder type and charge weight
- bullet make, weight, and whatever info you have on bullet seating depth or OAL.
- barrel length in inches
 
The rifle arrived yesterday and I had a chance to shoot it with these results using necked up .338 brass, Winchester LRM primers, Speer 235gr bullets and D4895SSC powder. Jethunter kindly ran a Quickload calculation for me that made me feel a lot better about all of this. I had also posted on 24CF and they'd suggested using starting H&H loads. The D powder suggested using IMR data minus 10% which put it right in the middle of a starting. 338 Win and .375 H&H data.

60gr - 2315FPS
61gr - 2366FPS
62gr - 2403FPS
63gr - 2438FPS
64gr - Error on Chrony
65gr - 2542FPS
66gr - 2572FPS
67gr - 2605FPS
68gr - 2632PS

I was only able to shoot 25 yards, but as expected, it was just one ragged hole. I was hoping for an accurate load around 2500FPS or so, as all I have this fall are a bear and a couple deer tags...and though this is my first .375, I feel like it will suffice ;)

Thanks everyone for the help,

Cory
 
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