It's a 40mm grenade projectile. First link is for a urethane replica. Second link is for a complete dummy round.

Looks to be the business end of some sort of explosive ordinance that would normally have a shell casing with powder in it to fire it.. This one has already been fired but not detonated.. Depending on it's weight it could also be just an inert depleted uranium round that was fired. If it is an explosive type of ordinance I would be careful with it and consider taking it to your police bomb squad just to be sure it is safe.

References:

https://en.wikipedia.org/wiki/40_mm_grenade

Reason:
Hey thanks for your answer. You are right. But, as we said before, your Paypal information must be incorrect. Please update your information so that we can send your bounty.

It's a 40mm grenade projectile. First link is for a urethane replica. Second link is for a complete dummy round.

References:

https://inertproducts.com/product/inert-replica-40mm-grenade-projectile/

https://www.worthpoint.com/worthopedia/40mm-dummy-round-40-mm-grenade-1860684775