And the diameter of the charge, which affects the required depth and thickness of the cone to achieve the Monroe Effect's focused blast. That can be counter productive to the aerodynamic shape required for effective flight, one reason why the WWII German Panzerfausts were short ranged, but very effective when they hit.
Additionally, the charge needs to be base detonated, though the noze fuze needs to be able to function even if it strikes the target at a less-than-ideal 90º angle. Typically, as in the Soviet PG-7 warhead or that of the M72 series US and British 66mm LAW rockets, that's accomplished with a piezoelectric crystal that provides a sufficient electrical charge to fire the charge's detonator when crushed into the target at flight speed. In the case of the RPG, the copper liner of the shaped charge is used as one electrical conductor to carry that electrical impulse for firing If the external body of the rocket is smashed into the charge liner, as when the rocket hits chail link fencing rather than solid plate, a short circuit of the firing circuit results and a dud round is the result. In practice, chainlink fencing will disable around 50% of the PG-7 rockets fired into it. M72 LAW rockets, being smaller, more often slip through, but are more often deflected, preventing a solid hit against the armor and thereby also resulting in a dud strike.
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