Could you elaborate on your 'spike' concept? It's not clear whether you are looking at pure penetration, or penetration AND expansion? The plastic tips in general are to assist with BC, cartridge feeding and in some cases to initiate expansion. The steel plunger on the Peregrine VRG3 & 4 is also there to initiate expansion - not to hold the bullet together or aid in penetration per se. The rationale is that the plunger is more reliable than the hollow point on say a Barnes TSX when it comes to ensuring expansion every time. It seems that you're thinking about some tough material (spike) that holds the bullet together? I would expect that in practise, such a spike would potentially cause the bullet to shatter. Any bullet with a lead core (or any core that's different to the jacket) runs the risk of separation, due to the differential hardness and malleability of the materials. Titanium and uranium cores are military designs for armour piercing - obviously these materials are typically restricted to the military and tend to be applied in bigger calibers (20mm and the like). Monos are the answer if you want a bullet that sheds minimal weight and stays together - the debate then is around the design/profile of the mono. If it's just DG penetration you're looking at then the Peregrine VRG1 & 2, the Dzombo solids and Northfork monos may be the solution you seek. Woodleigh hydro solids are also an interesting concept that may be applicable here.