Hi Aaron and welcome to the forum!
First, for safety’s sake, do you know if the shell is inert/empty?
Can you provide some measurements? Diameter at the base and overall length would be good. Also it looks like there may be some markings on the side if my eyes don’t deceive me. If they are readable posting those would help as well.
Like Larry says dimensions would be great. However at a glance it appears to be a British 76mm ARMDC TP-HESH projectile.