So I'm a bit confused-
I understand that a well designed bullet will deform upon having the heat and pressure from the expanding gas of the cartridges charge...This deforming will better seal the bullet to the bore and will allow less blowby- minimizing gas cutting. The bullet, or gas check, has to be soft enough to allow for this.
I also understand bullets with a full metal jacket do not expand in this manner, but rather are made to more extreme (tight) tolerances.
I was looking into using zinc for cast .223 as lead simply dissipates at any kind of speed, even with a gas check, and full metal jackets require swaging equipment.
My point of confusion is, I'm told zinc will wear a barrel very quickly... I look at the brinell hardness of zinc and it is in the realm of 400... I look at the hardness of copper and it is around 800... I don't disbelieve the experienced, I'm just confused as to why?