Plastic deformation

The one on the left was loaded over 17 grains of Lil' Gun. The one on the right was loaded over 13 grains of Lil'Gun. The one in the middle is not fired.If you exceed Lees Maximum pressure you will get Plastic deformation -------------------------------------------------------------------------------- http://castboolits.gunloads.com/showthread.php?p=35425#post35425 Quote: This whole relationship centers around the elastic limit for the alloy you are using and what the elastic limit is. the elastic limit is the point at which stresses can occur to an object and it will return to it's relative shape. Once you have reached the deformation stage it no longer returns to relative shape. this is a very simplified version of this topic as it pertains to engineering mechanics of materials. This is meant to be a guide and to keep you within safe/acceptable limits for pressure and alloy for your purposes. Obturated bullets do not mean that the shape has went through plastic deformation, just that it has expanded and stayed within the elastic limits of the alloy. The formula does not take into account other factors that aide in reducing friction and thus combined forces on the cast slug. As stated above, one member is getting very good accuracy with soft (by most peoples standards) alloys in high velocity loads (for cast anyway). Another factor not talked aobut is the pressure curve of the powder/cartridge combination. Does it spike quickly (fast pistol powder in rifle size case) or is it a gradual increase (full case of slower powder). Protection of the bullet base can also be a factor, we routinely do this by gas-checking, using lube wads, or fillers. http://en.wikipedia.org/wiki/Plasticity_(physics) plasticity describes the deformation of a material undergoing non-reversible changes of shape in response to applied forces Obturate means to block or obstruct.