I got a buddy that lives in Alaska. He emailed me about wanting reloading info. Quite frankly, I know nothing about the cartridge. Do any of the reloading manuals have a section on it, that I could pass the info on to my friend?

Mad Dog

The only manual that I found loads for the .375 Magnum Improved (Ackley) is in the Ackley manual. In that book Ackley states "There are several versions of this cartridge like the .375 Weatherby which are equally as good as the Ackley version."

In that book the loads for both the .375 Magnum Improved (Ackely) and the .375 Weatherby are ostensibly the same.

I have had a custom .375 Ackley Improved for many years made up for me by the late Floyd Butler and I have worked up loads on my own using both the data and my observations.

There must be data online.

The Barnes #1 manual has data for the 375 Weatherby which is close to the 375 H&H AI.

There is some data for the 375 Weatherby on Accurate Reloading.

John Ricks rebarreled a 700 for me with a 20", #5 SS Pac-Nor and I stocked it in a piece of Turkish walnut. It is likely the most accurate rifle I own. With 5/16" of cast at the heel and 1/4" at the toe and about 8 1/2# it is a kitten to shoot.

I have used it for a Kodiak bear (with Rick Bin and Muley Stalker) a number of deer and at least one black bear I can remember. I have been shooting 270gr XFBs in it and will change to the same weight TSX when the box runs dry. I have never recovered an X from it.

I get just a hair over 2700 with 74gr of IMR4064 in cold weather. There was no such thing as load development as the rifle is extremely forgiving. Though, it does not like the Failsafes I tried, at all!
art

Not knocking the AI, (I have two AI chambered rifles...a 257 AI and 7X57 AI), but why would someone decide on the AI, instead of the 375 Wby? This isn't meant to slight the AI and is asked as a serious question for my edification.

375 Wby ammo is still around a bit, and brass, too, FOR A PRICE. I'm glad I have all I'll ever need.

Brass is cheaper and the sharp shoulder makes the brass last forever... No stretching at all it seems.

PO said he thought the 7x57 was the best AI example, so you should see all the good if anyone can!

I have had two Ackley's and one Wby. There is one significant difference. The Wby chamber is cut about .02" shorter than the H&H and the Ackley, which are both the same. Occasionally you cannot chamber uncrimped 375 H&H in the Wby chamber whereas you can in the Ackley. This is only an issue if you are in some remote location and are stuck with the H&H handloads (most factory H&H ammo has enough crimp to enter the Wby chamber). If an H&H is rechambered then there is no issue either. The throating of the Wby is a little longer too. Both are pretty much wildcats so I would get the Ackley cause it looks wilder.

I shoot a 375 Weatherby , but if I had a 375AI I would use starting loads for the Weatherby(Hodgdon has data) and work up . Top loads should be lighter because of maybe no freebore in the AI chamber . I would expect 2900+fps for 270 grainers and 2700+ for 300 s , with powders in the 4350 range .

I do love the 7X57 AI I have in a re-chambered HVA. I also had a 7X57 I.C.L. Tortilla a while back; same thing but with a 45 degree shoulder.

I've not had much problem with the 375 Wby brass stretching, but my 300 Wbys stretch the pizz out of brass. The 375 is a re-chambered FN action Sako; it has just a bit less freebore than a Weatherby, and I get good velocities using mid Wby loads.

I use the 375 wby load data for my AI, It will shoot a 270gr Tsx to the same point as a 270gr h&h in my rifle.
Charlie

Any idea what the difference is between the 375 AI and the 375 Ackley Magnum is? PacNor lists them both?

375 Ackley Magnum

375 Ack Mag Imp

There several iterations of the "improved" 375 H&H, among them the Wby, the Ackley Imp., and the less often mentioned, the 375 Mashburn. I had the latter in a Ruger Tropical for awhile. And there are probably some I don't know of but all give roughly the same increase over the H&H.

In the past I just compared three or four reloading manuals to get a handle on what a top or near-top load for the H&H was (and compared it to the top in this rifle also as I shot it as an H&H for awhile before rechambering) and started there for the Mashburn and worked up a bit. As I recall, i experienced an increase in velocity of 100-175 fps over the old warrior depending on powder and bullet weight. Sorry, I don't have those notes any more so can't be more specific.

I have a M-70 in 375 AI, I used RL-17 to power 270 gr TSX's to 3100 fps looking for excessive pressure, never found it and suspended experiment at that level, backed them down to an even 3000 fps, accuracy is a bit over an inch for 3 at 100 yards.

Your friend can start at 83 grs of RL-17 and work up if you wish, that will start you in the neighborhood of 375 H&H performance.

Gunner

That's some awesome performance right there. Seems like a neat one and pretty relevant if you didn't want a WBY.

How do your rifles shoot standard 375 loads? Just wondering how they would shoot if you needed to run some in a pinch.

I have never fired factory H&H ammo in my rifle although I've heard it works well.

I seat 235 gr Speers very long and fireform with RL-15, the fireform loads are plenty accurate enough to hunt deer out to 250 yards or so if you wanted to.

Gunner

Thanks for the word Gunner. Thinking I wouldn't mind one built on a M70 either!

It's a dandy, mine is a put together model, I blew the throat on my M-70 7mm STW Laredo, saved the action and had a Smith screw a stainless factory barrel in 375 H&H that he had reamed to 375 AI, had a beautiful walnut stock built for it and even bought some very nice stainless bottom metal from Dirtfarmer here on the fire.

It's a one piece at a time kinda rifle, but that ornery bitch delivers a very serious reply.

Gunner

That's pretty similar to what I wanna do as well

10-4, Good luck, it's was a fun build.

Gunner

Thank you. I have a M70 338 that could be opened up and an H&H mag box put in. Might need to call my smith.

It would be hard for me to break down a good .338 WM. lol

Gunner

Same here Gunner. I would have never thought of it in the past, but my wife surprised me this past Fall with a Pre64 Model 70 338 Win Alaskan.



So, my M70 Classic is sitting at a gunsmiths right now. Waiting on some kinda barrel. Haven't ordered a barrel yet, but this seems like a great idea to me. I wouldn't ever get rid of the rifle, as it has a big past with me, but it won't get used much with the Pre64.



Thinking a 375 would give it a new lease on life?

SWEET, with the pre-64 Alaskan in your mitts let the breakdown commence , that NH 338 would make a fine all weather/all game 375 AI.

And the Montana slings are something else we have in common, nice aint they.

Gunner

I think so too! I love the rifle, just not as much as the Pre64!

Yeah, those Montana's are the best slings I have used yet! I love their belts as well.

The 375 Weatherby cartridges fit in my 375 H&H AI. Obviously, the H&H does too. So, if I had to use factory ammo, either would work fine, I suspect. I had a box of 300 grain solid factory ammo (H&H) I paid $10 for (19 loaded and 1 once fired). A cousin that safari's a bit told me that was a poor bullet/load. It worked well for busting rocks and forming cases, however.

Why the AI? Because that was what it was when I bought it. I suspect that I bought it at a much lower price than if it were a standard H&H chamber. Besides dies came with the rifle. I'm not worried about what it will bring when it is sold, that will be one of my kids problems. From all the reading I've done the AI and the Weatherby are identical in performance. I have not had the experience to verify that.
The rifle I have is a pre-64 Model 70. The trigger is 3 lb and crisp. Shooting off the bench full power loads in it feels lighter than full power loads in the 375H&H I had. The 375 H&H went away. That stock on the M70 fits me to a "T".

I'll not likely go to Africa again. But this rifle might be used in Texas at a high fence ranch or maybe on a white tail doe. A guy just needs a rifle like this, just in case the opportunity rises. Meanwhile it's a fun rifle to shoot.

I have the AI version on a P-17 Enfield that Winchester made. I fireformed brass with 4198 and cast bullets - no case failures. I have yet to run full tilt loads thru it as I can't get the stock to fit me correctly. I'll play with it this winter, if it is still uncomfortable I'll pull it off and start again. Nice thread, got me motivated to do something with mine.

Once ya get the stock where you want it……you may, just may find that will be your only hunting rifle, unless you need something pretty specialized!

I too shoot cast bullets, or at least did……it’s been a while. I tend to push mine pretty hard with jacketed bullets or for the past 31 years or so. I do minimal sizing, only lightly “kissing” the shoulder enough to make chambering near effortless…..just a little resistance. I toss my brass after 10 firings. Maybe I could go longer if I annealed my brass. With components, especially brass getting difficult to get, I may start annealing, to hopefully extend my case life a bit.

My most recent load is with Barnes 270 grain LRX’s pushed to 3100 mv from a 24” barrel. I need to go out sometime soon at near zero temperatures to determine my velocity loss due to low temperatures!

Unless you plan on shooting at some pretty extreme ranges, I think that those LRX’s woul make a pretty darn good “all around” load for anything that I’ll ever hunt here in Wyoming! memtb

This is what my phone ap says with 250 gr TTSX

Bugger, The LRX’s are marginally slower….but have improved BC! Here’s my numbers, though the cold weather numbers may be a bit lower. memtb

Keeping 2000 FPS till 850 is carrying some mail and should expand that big sucker.

I hope to never “need” it at 850……but, it’s nice to have it available! 😉 memtb

With a 375 AI or 375 Weatherby you won't need a 338 Win Mag. A 300g .375 bullet at 2800 fps should do everything a 338 Win Mag can and more.

How many of you wankers shoot Ackley unimproved cartridges?

They all are till the firing pin meets the primer

I did not realize that was not a standard H/H that Leighton used. Cool.

😂 memtb

According to Barnes the 270 LRX BC is .449 not 541.

And lower the temps in fall- early winter to 40* or less in this area at 1200 feet ele. At 3100 fps is good for 500 - 550 yds for expansion.(+2000 fps)

Bob
www.bigbores.ca

If that is the case, the .424 of the 250 vs the .449 of the 270 would keep me using the 250 version.

Holy crap……I have no answer to that. I have no idea where I got that number. I can’t even say that I transposed numbers, or somehow got a line off.

I apologize to all for the bad info…..believe me when I say I’m a lot more disappointed than any of you! memtb

It still shouldn’t bounce all the way off at a 600 yard elk

Well, it took a bit, but I found my mistake. When making an updated chart, I saw and used the “corrected BC” from a previous chart. Dumb ……I know! memtb

Maybe not…..but it’s still embarrassing and very disappointing! memtb

The correct chart……..a huge difference! 🤦‍♂️ memtb

Just a few words of warning. 1. If you're thinking of re-barreling a Model 70 from .338 Win Mag to a .375 Ackley, Improved etc, you need to ensure that the stock that is on the rifle will take the increased recoil. The .338 wood stocks have one recoil lug and one-cross bolt. The .375's have two cross-bolts and are made heavier from the factory and that is just for a standard .375 H & H. Many stocks will eventually split with that increased recoil. 2. The .375 H & H is right at the upper end of where most hunters can shoot well due to recoil. Everyone thinks they can shoot a more powerful cartridge than the .375 H & H well, but very few actually can. Anything more powerful compromises most hunters' ability to shoot dangerous game well. 3. The .375 H & H is very popular partly because it feeds so well due to the sloping shoulder and narrow shoulder and tapered case. On dangerous game, that is an important attribute. Just sayin'...no need to shoot the messenger.

You are correct is all aspects…… and 2 or 3 hundred feet of extra velocity adds a bunch of additional recoil, especially so in the lighter .338 format. My rifle at 9 pounds is the same weight as my wife’s synthetic stocked .338 WM, and kicks pretty hard!

If the shooter goes with a good synthetic stock, that should alleviate the stock splitting issue. memtb

I dunno Scotty. Elk are armor plated....

Guy

Good thoughts! I've had two 375's, a Model 70 and a Ruger Number One. Both were great rifles, I kept the Number One. Toyed briefly with the idea of "improving" it and decided it was just fine as a standard 375 H&H with good handloads. It's enough for me.

Regards, Guy

I would agree - so I'll continue using the 250 TTSX.

Bob
www.bigbores.ca

I hate “light for caliber” bullets …..even in the monos. With the 270’s, the velocity and energy gains may not be much @ 8 or 900 yards, plus they’re also shooting great…..so, I’ll stay with them!

I only went to the 250’s after waiting years for Barnes to make a heavier, high BC bullet…..finally gave up, and bought a bunch of 250’s. Then, within a few years……Barnes brings out the 270 LRX’s 🤬. Seems I can’t win!

If I run out and can’t get any before I die…..I still have a bunch of 250’s to fall back on, and I still have the load data! 😉 memtb

HA! I guess so. It is pretty cool to see what everyone uses for elk though.

Not limited to elk…..it will offer adequate performance for deer, antelope, and the occasional coyote! It’s pretty a darn good choice for general hunting……maybe not so much for extreme range! 😉 memtb

According to these charts and sighting the rifle in at 2.5” high at 100 yards. The load with a 250TTSX at 3,000 fps should be “point blank” to 300 yards. That is just point where you want the bullet to hit +/- 3”.
Should be good for a fellow with one gun.

That's exactly how mine is set up.

Same here….. we (wife and I) have used a 300 yard zero on our hunting rifles for many years. Our rifles have pretty similar ballistics.

The “only” possible negative is overshooting small animals (fox, coyotes, ect.) at around 160 to 180 yards or so. If you’re cognizant of that and compensate by holding a bit low…..ya have a dead varmint! memtb

I shoot 235 gr. Barnes xbt bullets out of my model 70 Winchester stainless classic. I still have a good stock of the 235's , Barnes quit making them quite a while ago. Bastards. My rifle likes them the best, the 270 gr.'s run a close second. I've recovered just 2 bullets, one out of a Shiras moose and the other out of my biggest bull elk. Perfect spread petals.

I just sent a fellow some 35 Barnes xbt bullets and threw in a partial box of 235 grain 375 bullets. PM me and I’ll get you his info.

👍 This is how we can help fellow shooters….Kudos! memtb

My most recent load is with Barnes 270 grain LRX’s pushed to 3100 mv from a 24” barrel. I need to go out sometime soon at near zero temperatures to determine my velocity loss due to low temperatures!

I got the same speed with a 270 TSX in a Mod 700 BDL SS 24" 375 H&H reamed to the 375 Weatherby. It was one wickedly flat shooter! It reminded me of the 340 Weatherby for sure. I was influenced by reading about Hal Waugh (sp?) the Bear Guide in Alaska. He claimed he always had his 375 H&Hs rechambered to get more speed for the 270 he liked to use on Bears. I was privileged to take a few head of game with the 375 H&H with Barnes 235 X, the 300 Sierra SBT, and the 270 FailSafe. No doubt it is a real killer, but with monos, no bloodshot meat (to speak of) I also must mention that I too am a big follower/reader of JOC and I always remember him saying "every Rifleman should own/use the 375 H&H in his lifetime", or something like that. Well, there ya go! i don't own one now, but love them anyway.

Believe it or not, I just shot mine across the chronograph this morning….temperature was 30 F. I was supposed to get out when it was near zero…..didn’t get it done! 🤬 I got an average of 3018 for 3 shots. A pretty substantial velocity loss from 90+ F, which I expected as I’m loading with RL 17……not recognized as a temperature stable powder. memtb

I Have a .375 Wby built on a defiance rebel action on the way to me now. Can't wait to try it.