Monday, 20 February 2017

76 mm M7 Gun Trials


The conclusions of trials of American armour piercing-tracer M-62 shells against armour described in table #17 and illustrated in the graph shows that:
  1. The penetration quality of American 76 mm AP-T shells can, under favourable conditions (angle/distance), effectively penetrate targets (tanks, SPGs, bunkers) with armour up to 120 mm thick.
    The penetration quality of domestic 76 mm AP-T shells (blueprint #2-09038) allows for effective penetration of only 100 mm of armour under identical conditions to American 76 mm AP-T shells.Given identical thickness of armour and angle from normal, the quality of the American shell guarantees penetration from larger distances than domestic shells, 1000 m at normal and 300 m at an angle.
    The advantage in the quality of American M-62 AP-T shells is explained by a superior design, well selected materials, and thermal hardening of the shell.
  2. Compared to domestic shells (blueprint #2-09038), American shell hulls have better robustness in impact against armour.
    The condition of various parts of the hull after striking armour is worth mentioning. The tip of the hull, even after penetrating 100 mm of armour at 30 degrees, remains intact in most cases. The driving band and post-driving band sections are not destroyed, but the post-driving band section deforms, which prevents the explosive filler compartment from bursting. The shell has a good gradient of hardness along its length, the hardness chosen is optimal, providing good penetration qualities and satisfactory robustness.
  3. Convenience of the crew: The overall planning of the fighting compartment and assignment of functions to crew members is poor.
    In the SPG tested, the gunner cannot independently fire indirectly, the commander does not have constant and uninterrupted access to the loader by voice or signs, as he is on the other side of the gun and must use a wired communication device.
    The loader only has half of the fighting compartment available to him, which lowers the convenience of servicing the gun.
Overall conclusions:

As a result of proving grounds trials of the 3" (76.2 mm) American M7 gun in the volume of 415 shots (25 increased charge), the ANIOP deems that:
  1. The presented American self propelled gun, capable of firing armour piercing and high explosive shells, can be used to combat enemy tanks and armoured cars, suppress enemy strongholds, destroy lights obstacles, and enemy forces.
  2. During trials, all gun and recoil mechanisms worked satisfactorily.
  3. The muzzle velocity of the 6.75 kg M-62 AP-T shell with 2.095 kg of gunpowder (brand 12/7) and peak pressure of 2580 kg/cm² is 810 m/s.
  4. The gun stability is satisfactory.
  5. The precision of fire against a vertical target with the M-62 AP-T shell is satisfactory. Mean deviation was measured to be the following:
    1. At 500 m: 0.06 vertical, 0.10 horizontal
    2. At 1000 m: 0.14 vertical, 0.24 horizontal
  6. When firing the M-62 AP-T shell, the departure angle of the shell from the gun is almost zero.
  7. The maximum and practical rate of fire with shells kept in the ammunition racks is 4-6 RPM. When shells are kept outside of racks, the maximum rate of fire is 10 RPM.
  8. The penetration of the 3" (76.2 mm) American M-62 AP-T shell is shown in the table below.
    Armour type
    Angle (degrees)
    Minimum speed (m/s)
    Equivalent distance (m)
    75 mm homogeneous K=2400
    90 mm homogeneous K=2600
    100 mm homogeneous K=2250
    120 mm homogeneous K=2400
  9. Robustness trials of elements of the American 3" (76.2 mm) M-62 AP-T shells at increased propellant charge showed satisfactory results."


  1. Is this part of another study?
    Or a different vehicle?
    The gun has good precision. At a range of 1200 meters, average horizontal deviation is 0.16 meters and vertical deviation is 0.1 meters.
    This is also a 76mm gun.

    1. since they mention M7 gun it'll be some M10 TD but correct me if i'm wrong

    2. 3" M7 would mean the M10 GMC, yes. The M18 carried the related 76 mm M1A1/A2 series instead. Those used the same shells but different cartridges and the Metric designation was duly chosen to avoid logistical mix-ups.

    3. Yes, the M7 would be a 3" on the M10. The Hellcat would have either the M1A1, M1A1C or the M1A2 76mm gun. The muzzle velocity is different than US published values but some of that might be attributed to testing elevation differences.

  2. Some observations.

    I) Terminology. It´s not called "shell hull" but "shell body". "Tip" is not used, either. The uppermost point of a projectile is called "point", the upper third above the fwd. bourrolet is called "nose". It´s also worth noting that instead of "post driving band section" the term "base" is used in english language.

    II) the M62 uncapped monobloc solid shot AP-T had no explosive filler. Only a tracer element was inserted in the tiny cavity, this element does not "explode" and therefore cannot be prevented from "exploding" under conditions of base damage.

    III) the hardness gradient of the 76mm M62 AP-T was inferior under conditions of impact against 269BHN armor or high impact velocity to Pzgr39. The lateral shift of hardness was considerably inferior as demonstrated by frequent break up at 40°-45° obliquity.

  3. Uncapped M62 solid shot AP-T? You must mean the M79 solid shot AP-T.

  4. correct. M62 was capped (APCBC-T).