Projectile ballistic cap ID

[Burney Davis]

Can anyone ID this cap Please.

Of rough construction and no exterior marking. The internal threads are very course. Base diameter is 10cm and height is 20.4cm. TIA

 

[Fred]

Just a wild guess, but possibly the tip of a rapier missile?
fred

 

[Burney Davis]

Just a wild guess, but possibly the tip of a rapier missile?
fred

Thanks for the thoughts, but I think this is just too crudely made for a modern piece.