If anyone could help me identify this projectile it would be vey much appreciated. The research I have done leads me to believe it was ammunition for the 1.1"/75 (28mm) Mark 1 and Mark 2 WWII era anti-aircraft gun (also known as the “Chicago Piano”). The caliber is correct but the length and weights do not match the descriptions for the weapon’s ammunition on this site: http://www.navweaps.com/Weapons/WNUS_1-1-75_mk1.php This site shows the length of the projectile at 5.8" and a weight of 0.917 lbs.
Measurements taken with a caliper:
1.109" at the base (below the rotating band)
3.455" total length
7.995 oz. total weight
Rotating band material is copper
Is it possible that this is a practice round for the Mark 1 or Mark 2 weapon?
Could the different corrosion at the tip be an indicator of the munition type? My uneducated guess is that it has something to do with a cap that was once on top the round, like an armor piercing cap (APC) like what is described on this site.
Any insight at all or any reference material that you can provide would be very helpful. I have more photos if that helps but I can only post 1 at a time on this board because I am a new user. Thanks everyone in advance!!