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USN 20x197 test round
- Thread starter SG500
- Start date
Another of those unusual rounds made from a 1.1 inch USN case.
First photo shows a regular 28x199SR case to the left with the 23 x 146SR round to the right.
Second photo shows the 28 x 199SR head stamp to the left and the 23x146SR headstamp to the right clearly showing ".90cal T1"
Ref Tony Williams excellent book "Autocannon: A History Of Automatic Cannon And Their Ammunition" page 128......."For the US .90 cal aircraft gun projects in the late 1930's. Unlike the latter T2-T4 series, the T1 was designed to achieve a higher muzzle velocity so the brass, semi rimmed case is bigger. It was based on the USN's 1.1 in ch case, shortened and necked down with a particularly long and tapered shoulder. Overall round length is 222mm and weight c.530g. Projectile weight is 204g and MV was 869 m/s."
First photo shows a regular 28x199SR case to the left with the 23 x 146SR round to the right.
Second photo shows the 28 x 199SR head stamp to the left and the 23x146SR headstamp to the right clearly showing ".90cal T1"
Ref Tony Williams excellent book "Autocannon: A History Of Automatic Cannon And Their Ammunition" page 128......."For the US .90 cal aircraft gun projects in the late 1930's. Unlike the latter T2-T4 series, the T1 was designed to achieve a higher muzzle velocity so the brass, semi rimmed case is bigger. It was based on the USN's 1.1 in ch case, shortened and necked down with a particularly long and tapered shoulder. Overall round length is 222mm and weight c.530g. Projectile weight is 204g and MV was 869 m/s."
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