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350 gr .375" SMK Load Data?

I'm seeking load data for the 375 Rem Ultra with the 350 gr Sierra Matchking. Sierra doesn't have any yet and none of the powder suppliers (Alliant, IMR, H, Win) list any. Has anyone worked up a load on this? I have obtained very good accuracy with H4831 and IMR7828, but I haven't had opportunity to chronograph them and with the shortage of brass, things have been on hold until I don't have to cry over every worn case.


  • babunbabun Member Posts: 11,064 ✭✭✭
    edited November -1
    How does your loads compare to the .375 ruger round. It has load data for 350 grainers. The Ruger has 10% less case capacity. So loads listed for it should be on the light side for you.
  • Ray BRay B Member Posts: 11,822
    edited November -1
    Using a Powley Computer (slide rule) the calculated load is 93 gr of 4831 for 2530fps (from a 28" bbl) at 46,000 psi. This is considerably more than the data shown for the 375 Ruger. the Heaviest loads that I have used so far have been 87 gr H4831 and 87 IMR 7828. They are both accurate to 300 yards, which is as far as I've had the facilities to shoot from a bench. My suspicion is that the velocity is about 2200fps which won't be stabilizing that long bullet and that when I'm able to shoot it at 600 yards the accuracy will become a pattern rather than a group. the pressure indicators are still very mild, so it may be possible to reach the Powley data, but I hate to wear out my small hoard of brass seeking to find a long range load.
  • MG1890MG1890 Member Posts: 4,649
    edited November -1
    I doubt you could get enough 4831 in the case to cause trouble.

    If you haven't already, get some bushing style dies. Your cases will last a very long time if you don't ovepressure and stretch the primer pockets. You will also much improve long range accuracy.

    Oh, and Federal 215M's.
  • nononsensenononsense Member Posts: 10,931 ✭✭✭✭
    edited November -1
    Ray B,

    There are a couple of things not being addressed with your problem.

    What is your OAL with this bullet based on your chamber length?

    If you're not chronographing these then why waste the powder, bullets and wear?

    Standard OAL with this bullet is 3.600" which seats that bullet 1.000" into the case losing you something on the order of 26 grains of capacity.

    The loads you've tested appear to generate 2400 FPS approximately which will require a 1:14" twist rate by rough calculation.

    The Powley Computer, while a marvel of ingenuity, will not generate the proper balance of powder given the case capacity and pressure ceiling. It also leaves out some very useful powders from other manufacturers. Call Sierra and talk with the ballisticians to get appropriate data for this bullet.

    Given the OAL of 3.600, Norma MRP is the velocity winner at 2670 FPS approximately. IMR-7827 SSC is on it's heels at 2650 approximately. Re-19 should get you to 2600 FPS. These are all based on a 28" barrel for comparison. None of these exceed 62,000 PSI. If your chamber is cut correctly it should have minimal resizing for this cartridge and bushing dies will help with longevity so long as you remember to resize the body when the cases get tight...

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