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    Hunter Arms Pressure Curve 6-10-1929 Archived Message

    Posted by Drew and Gary on January 5, 2017, 8:25 am

    Many thanks to Gary Rennles who has been reviewing the digital images in the McCracken Research Library, Buffalo Bill Center of the West.

    The image can be magnified with good resolution by clicking here
    http://library.centerofthewest.org/cdm/singleitem/collection/WRAC/id/8149/rec/107

    The original graph is part of the Winchester Repeating Arms Company Collection, but includes a notation “Hunter Arms Co”. WRAC was not acquired by Western Cartridge Co. until Dec. 22, 1931 so it is impossible to know if the curve was generated by Winchester, Western, Hunter Arms or (very possibly) the Burnside Laboratory of the E.I. du Pont de Nemours & Co.



    PROOF LOADS
    Loaded with FFFg black powder. Shot presumed to be No. 6
    Pressures measure by crushers (LUP - Lead Units Pressure) and modern piezoelectric transducer measurements would by 10 – 14% higher
    F - 10g 2 7/8” 9.5 Drams with 2.36 oz. shot = 16,000 psi
    A - 12g 3” 8.265 Drams with 2.187 oz. shot = 17,250 psi
    G - 12g 2 3/4” 7.53 Drams with 2 oz. shot = pressure not recorded
    B - 12g 2 3/4” 6.5 Drams with 1.687 oz. shot = 14,200 psi
    C - 16g 2 9/16” 6.5 Drams with 1.687 oz. shot = 13,750 psi
    D - 20g 2 3/4” 5.74 Drams with 1.5 oz. shot = 14,625 psi
    E - .410 2 1/2” 2.377 Drams with .624 oz. = 15,625 psi

    LTC Calvin Goddard writing in “Army Ordnance” in 1934, stated that Hunter Arms proof tested 12g 2 3/4” chamber barrels at 14,300 psi.

    MAXIMUM STANDARD LOADS
    1” peak pressures
    H - 12g 3” ‘Record’ 1 3/8 oz. shot presumed 1275 – 1295 fps = 13,250 psi
    I - 12g 2 3/4” ‘Field’ 1 1/4 oz. shot presumed 1330 fps = 10,750 psi
    The label ‘J’ for 28 gr. Ballistite and ‘K’ for 3 1/2 Drams DuPont Bulk appear to have been switched on the pressure curve graph. Dense Ballistite clearly generated greater pressure than DuPont Bulk.
    K - 12g 2 3/4” 1 1/4 oz. 28 gr. Ballisitite = 12,900 psi
    J - 12g 2 3/4” 1 1/4 oz. 3 1/2 Drams DuPont Bulk = 10,000 psi
    The pressure curves essentially met at 5” at 7000 psi; at 10.1” 2625 psi (DuPont Bulk) – 3000 psi; at 15.5” 2000 psi; at 22.1” 1500 psi

    Progressive Burning DuPont Improved Military Rifle (I.M.R.) Powders were introduced in 1914. DuPont Oval was developed for the 1922 introduction of Western Cartridge Company’s 12g ‘Super-X Field’ 2 3/4” 1 1/4 oz. 3 3/4 Dram Equiv. shell. The Peters Cartridge Co. ‘High Velocity’, United States Cartridge Co. ‘Ajax Heavies Long-Range’, and Remington Kleanbore ‘Nitro Express Extra Long Range’ (the boxes were marked “3 3/4 Drs. Equiv.”) loads soon followed.
    Western’s 3 inch ‘Record’ with 1 3/8 oz. of shot was released in 1924.

    Western Cartridge Co. never marked the Super-X ‘Field’ or ‘Record’ boxes with “Dr. Eq.” stating only “Maximum Load”. It is presumed that 12g ‘Super-X Field’ 2 3/4” 1 1/4 oz. was 3 3/4 Drams Equiv. or 1330 fps, and the 3” 1 3/8 oz. ‘Record’ was 1275 - 1295 fps (the speed of 1 1/4 oz. 3 1/2 Dr. Eq. loads).

    In a 1927 Western Cartridge Co. flyer “Super-X The Long Range Load” by Capt. Chas. Askins the 12g “Duck Load” (not specified but presumed to be 1 1/4 oz. Super-X ‘Field’) is described as 3 1/2 dram (38.5 gr. powder; also not specified but no doubt DuPont Oval) at 1400 fps (at the muzzle rather than 3 feet) and fps at 40 yards, with a breech pressure of 3 3/4 tons or about 11,480 psi by Burrard’s conversion.



    From the 1928 edition of “Smokeless Shotgun Powders” by Wallace Coxe, ballistic engineer of the Burnside Laboratory of the E.I. du Pont de Nemours & Co. “DuPont Oval can be loaded with 1 3/8 ounces of shot in a 12-gauge shotgun to develop the same velocity and pressure as obtained with a load of 3 1/2 drams of DuPont Bulk Smokeless Powder or 28 grains of Ballistite and 1 1/4 ounces of shot. The relation naturally holds with other charges, but as DuPont Oval is used principally for maximum loads the comparison is more striking as it shows the possibility of using a heavy load with DuPont Oval that would be an abnormal load were it used with DuPont Bulk Smokeless, Ballistite, or other existing old-style types of shotgun powders.”
    Coxe reported 3 1/2 Dram Eq. 1 1/4 oz. loads (1275 fps) and 40 yard fps:
    NOTE: pressures were measured by crushers (LUP) and modern transducer measurement pressures would be 10 – 14% higher
    DuPont Bulk smokeless powder - 11,700 psi, 943 fps
    Schultze Bulk smokeless powder - 11,800 psi, 941 fps
    28 grains of Ballistite Dense smokeless powder - 12,600 psi, 966 fps
    Note all 3 are greater than the SAAMI 12g 2 3/4” recommended maximum pressure of 11,500 psi.
    40 grains of DuPont Oval Progressive Burning powder - 9,400 psi, 981 fps

    From “Smokeless Shotgun Powders: Their Development, Composition and Ballistic Characteristics” by Wallace H Coxe; E.I. du Pont de Nemours & Co., 1927, a DuPont Oval Pamphlet, p.20.
    Dram Eq. is listed on the graph as 3 but is more likely 3 3/4 compared to the 1928 data.
    Charge was 1 1/4 oz. Pressure is expressed in Long Tons.
    Using Burrard’s estimated Tons Lead Crusher Pressure (Cp) conversion to PSI (pound force per square inch): (Cp x 1.5) - .5 = TSI; TSI X 2240 = PSI
    Ballistite maximum pressure at 1” was 4.9 Long Tons = 15,344 psi
    Schultze at 1 3/4” was 4.5 Long Tons = 14,000 psi
    DuPont Bulk at 1 2/3” was 4.1 Long Tons = 12,656 psi
    FFFg at 1 1/2” was 3.8 Long Tons = 11,648 psi
    Note all 4 are greater than the SAAMI 12g 2 3/4” recommended maximum pressure of 11,500 psi.
    DuPont Oval at 2” was 3.5 Long Tons = 10,640 psi
    All the curves essentially meet at about 3 1/2”.




    I would of course appreciate any corrections or clarifications of my assumptions/interpretation.
    At least we can now KNOW the proof pressures used by Hunter Arms.

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