Home Forums Hunting & Shooting Express Rifles and Big Bores Only 375 H&H AI loads

I posted this in big game rifle reloading and thought it better here:

From wikipedia

"The case capacity of the .375 Ruger is 99 gr. of water (6.42 cm3) .
The 375 H&H Magnum has a case capacity of 95 gr. of water (6.16 cm3), an increase of 4% for the Ruger
Case Capacity of the 375 Weatherby Case is 105 gr. of water (6.82 cm3) an increase of about 11% over the H&H and 5% over the Ruger. (the FreeBore/Leade for the Weatherby is 0.373 thou. as per the Factory Spec's"

I believe the case capacity of the 40 degree 375 H&H AI is marginally greater (in my rifle) than the 375 Weatherby, by how much I don't know, (300 Weatherby ammo chambers in my AI - I have not fired any Weatherby in my rifle, but have H&H. I don't have any 375 Weatherby ammo or brass.)

I've not found a lot of data on the 375 H&H AI, I have various bullets 200 grain to 300 grain Jacketed and a few cast bullet molds. I am concerned with using Weatherby 375 load data due to Free Bore in the Weatherby.

I'm thinking 3,000 fps with 235 grain to be about top, maybe 2,800 fps with 270 grain, and 2,700 fps with 300 grain. The lighter bullets and the cast bullets will be for practice off-hand shooting.

I plan on working with this rifle this Winter if the weather cooperates.

My 375 H&H AI has a 26" barrel.

Tag this. I have the metal done, but wood is not fitted yet. I used a '17 Enfield action.

In my .375 AI, 24” barrel - 250 TTSX’s @ 3130 fps. I went to higher velocities, but the groups were starting to open up! 3 shots under 2” @ 300 any time I do my part! Running Winchester brass, Fed. 215 primers, and RL17 for fuel! memtb

memtb - how was your case life? The 7th edition of the Hornady Manual reports maximum velocity with 225 grain bullets to be 3,000 fps with 24" barrel in the 375 Weatherby. Not discounting your load at all, just curious. I'm on the traveling up side of the learning curve - at least I hope to be.

Bugger, I’m not certain on these. My previous loadings were, 270’s @ over 2900.....I was discarding @ 10 firings! It’s possible (though unlikely) that I may have gotten more, had I taken better care of my brass! With my present loads, I’m only at around 5 firings .....so far! memtb

RE17 - I didn't think I had any of this powder. I checked and I do. I'll have to try it.

I had (I believe) it was a Whitworth 375 H&H and I sold it as the stock didn't fit me quite right. The Pre-64 Winchester 375 H&H AI stock fits me better and I can shoot full power loads in it easier than with the standard 375 in the Whitworth.

I looked and I have over 100 loads loaded for that Whitworth. I guess those loads are fire forming loads now.

What have you used for fire-forming?

I pulled the 24 inch stainless barrel off my classic stainless 375 AI, the thing shot too good to rebore to 458, 235 speers, 270gr tsx, 300gr partitions and a-frames, it shot them all, I have the barrel and a set of Redding 375 AI dies if anyone has interest.

You can get an easy 3000 fps with RL-17 under a 270gr TSX.

My 375 Weatherby with 24” barrel gets 2960fps with a Nosler 260gr Accubond, 2900fps with 270gr Woodleigh and 2830fps with 300gr Woodleigh. These velocities have been verified from drop and 4 other chronographs.
They are NOT my regular loads, have actually dropped all of these down a grain of powder for brass life reasons.
I had one reading of the 260gr Accubond at 3002fps, which I disregarded during testing, but when I purchased new bullets and 760 powder, with the same load during re-work, I registered 3 rounds at 2999, 2991 & 2994fps, so the 3000fps is probably feasible, but brass life will be short.

Cheers.

I found cast bullets I cast for my 375 Whelen AI and my 375 Win. I have used Bullseye with the lighter cast bullets and I'll try 5744 with the heavier bullets. I'll record velocities and also use them for case forming. I've got about 150 cases fire formed now. I think most of the rest will be with cast bullets.

have a re chambered Winchester push feed cut to Weatherby dimensions , my speeds run pretty much the same as 416 Rigbys


right at 3000 with 260gr Accubombs and Ramshot Hunter


2900 with 270gr Hornaday spire points and H4350


Weatherby factory ammo with 300gr Noslers with run 2800

There was no wind today, overcast and 27 degrees Fahrenheit - nice day in SD and perfect for load testing, I think. (In SD the wind is calm when it's changing directions.)

My Caldwell Chronograph gave me some fits, I'm thinking I'll have to upgrade. The first 4 or 5 shots I couldn't get it to read then...

My fireforming loads of 85 gr H414 behind a 270 grain RN (MidwayUSA seconds - Hornady, I think)
2736, 2714, 2729, 2704, 2688 fps ave 2,714 fps, 48 fps or 1.7% spread

33.5 gr A5744 286 gr cast
1673, 1687,1666, 1686, 1691 fps ave 1,680.6 fps, 25 fps or 1.4% spread

5 gr Bullseye 238 gr cast (with muzzle raised before shot)
1720, 1725, 1732, 1759 fps ave 1,734 ave, 39 fps or 2.2% spread
without raising muzzle 1464 FPS

The chronograph had fits with 300 gr Remington solids loads for some reason, after 6 shots, I only got one reading = 2521 fps (what's error 3?)

The grouping was pretty good, except with the "not muzzle raised Bullseye" load and the following...

The scope may have given up the ghost with the last 6 rounds tested - the 300 grain factory solids since the height spread was over 30 MOA and the bullets landed 12 MOA to the left. It was, I thought, the perfect scope for the rifle -- a 4x M8 Leupold with cross hairs and German post and Leupold quick release bases and rings. I'll put a different scope on it before taking it out for round two, but that's enough for today. Yes the mounts/rings are tight.

I may be sending that scope back to Leupold if everything checks out. I'll have a second scope sighted in with Leupold quick release rings when I take it hunting.

What scopes are you guys using on your 375's?

I used a Leupold 2.5-8 on my 9 pound .375 AI, for over 20 years, then went to a Leupold 3.5-10 CDS! I use Leupold QR base/rings.....the 2.5-8, is “suited-up and waiting on the sidelines”, if ever needed! memtb

Bugger, I use a Vari X 3 1.5 x 5 on my Whitworth. Mb

I have a Vari x 3 looking for rifle to sit on. game. I was thinking that would fit my “new to me” 300 H&H pre-64. It will likely be on the 375 next now and one of the two for that the rifle when I get to use it on game - I’ll be using that M8 again when it’s returned from Leupold. Maybe the third scope will be the second scope for either rifle. I got extra quick release Leupold rings coming...

Alas, I will still need a third scope.

Thanks.

Shirt sleeve weather in NE South Dakota today. Sunny and 37 degrees Fahrenheit. The chronograph worked better too, only one error 2.
270 gr Fire forming load H414 85 grain with WLRM primer and WW brass - 2715 fps

Then switched to Nosler brass H1414 270 grain RN WLRM primers
2747
2741
2761
2739
2740
average 2745.6 fps, 21 fps or .7% spread (I should have noted the fire forming loads on the 1st had a mixture of primers)
I had another 300 gr solid and it registered 2760fps

Now for trying to reach 2,800 fps and not reach too high of pressures. Hornady manual shows 2,800 fps as maximum for the 375 Weatherby and 270 grain bullets.

270 gr rn (Hornady seconds I think) seated so the the crimping grove on the bullet was at the end of the case. 3.59" COL, Federal 215 Primers, Federal Nickel plated brass, 85 grains of H4350
2760
2769
2771
2740
2780
2,764 fps ave, 40 fps0r 1.4% spread

270 gr sp Interlock seated so the the crimping grove on the bullet was at the end of the case. 3.507"" COL, Federal 215 Primers, Federal Nickel plated brass, 85 grains of H4350, this time a mild crimp was included:
2861
2797
2817
2847
2783
2790
2,815.8 ave, 71 fps or 2.5% spread

A mild load was tried, kicked liked a 243 varmint load, 42 gr H4895, 235 gr Speer Hot Core Rem 9 1/2 Primer, WW brass
1902
1915 (hang Fire)
1800 Raised muzzle first
1771 Raised muzzle first
1719 Raised muzzle first
1,821.4 ave, 196 fps or 10.7% spread

So far for this test, I've fired close to 200 loads including all the fire forming loads. The Nosler, & WW brass has held up well. The WW brass was new, the Nosler brass was fired maybe once fired, before fire forming. I'm not sure about the FC brass.
Most of the Remington brass has been fired a few times before in a 375, how many, I don't know but see the picture, I've had three such failures with this brass. I am annealing all the brass because of this and so that the brass will as good as possible for comparison. There was one failure on the neck of a FC brass too.