Load Data For .375 H&H (P.O. Ackley Improved)

Discussion in 'Reloading' started by bohemian, Jun 5, 2011.

  1. bohemian

    bohemian New Member

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    Looking for Load Data For .375 H&H (P.O. Ackley Improved)

    have not had any luck so far finding any load data yet.

    thanks in advance.
     

  2. sestoppelman

    sestoppelman AH ENABLER AH Ambassador

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    According to Ackley himself, the 270 gr bullet is maxed at 81 grs of 4064 for 2830 fps. The 300 gr is maxed at 78 grs of the same powder for 2630 fps or 88 grs of 4350 for 2740 fps. List also the 350 gr bullet at 88 grs of 4831 for 2650 fps. There is other info out there just by Googling.

    Have fun!
     
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  3. bohemian

    bohemian New Member

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    thanks for the info, while I found plenty of general historical info googling I was amazed at how difficult it has been to find any .375 H&H Improved (P.O. Ackley) load data on the internet... I don't know maybe my google fu isn't quite up to snuff for this kind of search...
    Any suggested links would also be most welcome...

    Is there a cartridge over all length with and without a seated projectile listed in the P.O. Ackley information you have?
    Is the 4064 you itemized IMR 4064?

    thanks in advance.
     

  4. sestoppelman

    sestoppelman AH ENABLER AH Ambassador

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    None of the powders listed specified but I can pretty much tell you that in that era, IMR was the only 4064 and 4350. The 4831 could be either H or IMR but no mention. My guess would be IMR again per the era.
    As to lengths, no mention in Ackley however in my Manual of Cartridge Conversions it shows: Case length at 2.83 and OAL at 3.75 inch. Of course that could easily vary somewhat as to actual chamber dimensions of the rifle.
    Were it me I would limit my powders to the slower ones, 4064 is good stuff but full velocities wont be realized before pressures exceed max.
     

  5. bohemian

    bohemian New Member

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    ok, thanks again.

    interesting that the c.o.a.l. is so much longer than the parent .375 H&H c.o.a.l. I found on barnes site...

    they have 3.545"-3.575" for c.o.a.l. depending on projectile used...
    and 2.840" for c.l.
     

  6. Adventure_Hunter

    Adventure_Hunter New Member

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    We have a 375 Ackley Improved that we inherited and I am wanting to sit down at the bench and load some 300 Grain Swift A Frame bullets.
    Does anyone have a good "starting point" for a load and then a "maximum load"?

    I see above someone listed:

    Bullet: 300 Gr
    Powder: 88 grains of 4350 (which 4350?)
    Velocity: 2740 fps.
    OAL: Case length at 2.83 and OAL at 3.75 inch

    This looks to possibly be a very hot load. We want to find a safe load with a velocity around 2600 fps that isn't pushing the limits.
    We want lower pressures.

    Love to get a reliable load. Any help would be appreciated.
     

  7. Bullthrower338

    Bullthrower338 AH ENABLER AH Legend

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    loaddata.com lists several loads the 88.0 grain load for a 300gr soft is for IMR- 4350 with a published velocity of 2740, lists 300gr soft with 85.0 gr of IMR-4350 at a velocity of 2650.

    PM me your address and I will email you a good article on the 375 H&H AI
     
    Last edited by a moderator: Nov 29, 2018

  8. limpopo

    limpopo AH Member

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    In my Barnes Reloading Manual #3, lists loads for the 375 Weatherby, 235-300 grain weights. While not the Ackley Improved, the Weatherby is an Improved in it's own right. If haven't got a copy, shoot me a PM and I'll try to scan the pages etc. Hope this helps.
     

  9. 450 Dakota

    450 Dakota AH Senior Member

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    Starting load data for the 375 Weatherby is a good place to start as Limpopo said. Case capacity is real close the pressure differnce, for the most part, will come from how much freebore you have vs the Weatherby.
     
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  10. JimP

    JimP AH Elite

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    I would just start with the loads for the 375 H&H near the top of the hotter ones and just work up from there. That is if you can't find data for the 375 Weatherby since the Weatherby is considered the AI version. Also to find load data do a search on the 375 Weatherby and you will finds lots of information on it along with the AI version.
     
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  11. Milehighshooter

    Milehighshooter AH Enthusiast

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    Loads for the 375 Wby and the 375 JRS should work. They're all about the same
     

  12. Ray B

    Ray B AH Elite

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    years ago I had some correspondence with bill Steigers who was doing some load development with the wildcat 375/8mmRem Mag, which seems to me was later claimed by Jon sundra as the 375 JRS. Bill's wild cat was the 8mm rem Mag with the 25 degree shoulder, other dimensions the same. It looks like you have plenty of load data listed above, but I'll check back through my files and see if I can locate the data that Bill sent.
     

  13. meigsbucks

    meigsbucks AH Fanatic

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    Load data for both the .375 Wby and the .375 JRS are in the old A-Square load manual: Any Shot You Want.
    For the JRS they show 80-84gr of IMR 4350 behind a 300gr monolithic solid.
    For the Wby they show 84-88gr of IMR 4831 behind a 300grDeadTough.
    They show other powders as well.
     

  14. wswolf

    wswolf New Member

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    I had a .375 Ackley Improved a long time ago. I don't recall any specific data but the the velocity increase over the H&H was miniscule. The data in PO.'s Handbook was way too hot. The first load I tried with IMR4350 was 5 grains below the maximum load listed and still blew the primer plumb out of the case! Weatherbys are chambered with a lot of freebore between the bullet and the start of the rifling so Weatherby data will produce much higher pressures in rifles with less freebore. According to my calculations the Ackley case volume is about 6.8 % greater than the standard H&H so has the potential to produce about 1.7% higher velocity. I would start with .357 Ruger or H&H data and not try to exceed the highest published velocity with a given bullet.
     

  15. Paul Homsy

    Paul Homsy AH Veteran

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    I realize how old this thread is but I'd like to provide my experience.
    Close to 30 years ago I had a gunsmith open up a 375 H&H for an improved of my specifications. The increase in powder capacity is very similar to the 375 Weatherby and A.I.
    My starting point for loading was the load data for these two cases. The resulting speeds surprised me.
    Today's powders would have simply not encouraged me to improve the chamber of my rifle as they are very efficient.
    Suffice it to say that without excessive pressure, the average speeds I obtained were as follows:
    1) Nosler 260 grains partition, 3060 fps
    2) 270 grans Fail Safe, 2950 fps
    3) Nosler 300 grains partition, a hair over 2800 fps.
    All loads chronographed with an Oehler 33 and an Oehler 35 P. Twice and with a friend's 35 P.
    Barrel, 24 inches.
    I do not wish to provide the loads as this is an individual rifle thing but if all you're getting are the speeds listed in the above posts, you aren't using the right powders. Quite frankly, I never expected to achieve these speeds, in fact nowhere near...Use slow burning powders with magnum primers. I used Winchester magnum primers.
    I obtained some of my best results with Reloader powders. Reloader 19 for bullets up to 260 grains and Reloader 22 for heavier. Go safely, every single improved rifle is different but to only obtain 2650 fps with a 300 grains bullet after the improvement is a total waste. These are speeds easily achievable in any properly reloaded standard 375 H&H.
    Before the improvement, I obtained 2750 fps with Speer 270 grains bullets, a regular boatail. (I didn't chronograph the 285 GS)
    And also obtained 2700 with Sierra's 300 grains boat tail which is a bullet with minimal bearing surface. This definitely helped achieve higher speeds. These were hot loads but not excessively so. My point is that in the proper action, speeds achievable are not published. These were shot off the bench without a scope or muzzle brake. The rifle weighed 8.1/2pounds. The recoil was sharp but very tolerable and even with open sights, the groups were excellent. At the time I planned to use these bullets for North American hunting. I ended up using Partitions.

    The recoil of the improved cartridge is sharper as it becomes a high intensity cartridge while the 375 H&H is looked at as an "efficient" cartridge. Don't expect the shove most people describe the H&H as providing but rather a sharp strong recoil approaching and at times exceeding 416 Remington recoil.
    I had the barrel fitted with a muzzle brake and added a scope, both the added weight and brake made bench shooting quite tolerable for long sessions of 50-60 rounds. I don't hunt with the brake but I strongly suggest it for load development.
    Each rifle is very different. Before making an improvement, see what you can get with modern powders and a regular 375 H&H. IMR 4350 (old Dupont) used to be the go to powder. It's still excellent for the standard case but there are also others that weren't in use 30 years ago that are excellent, however the added speed, in most improved rifles, are achieved with Reloader powders.
    Barnes in their reloading manual #3 and Hornady in their current manual both offer load data for the 375 Weatherby, that particular information is a good starting point.
    Load Data online also has A.I. loads. A balance between the milder loads of these sources are the way to go.
     
    Last edited: Oct 14, 2019

  16. wswolf

    wswolf New Member

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    The 4831 in Ackley's manual would be military surplus from WWII. Its burning rate is reportedly slower than the modern H4831. IMR4831 has a burning rate between H4350 an H4831.
     
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