Mk318 bullets

AFAIK the mk318 bullets, the mod0 and mod1 have different core materials, the mod0 has a lead core and then the Army or somebody wanted a green bullet so they changed the lead out for an alloy of tin/bismuth?? I am guessing, not knowing jack about bismuth and little about tin, especially its weight, that if the core material of the mod1 is lighter in weight there would have to be more of it to maintain that 62 grains of weight. If my assumptions are correct and if they wanted to maintain consistent performance from mod0 to mod1 the jacket construction would have to be the same. So, where did they add the extra core material to maintain the weight? Is the mod1 bullet longer than the mod0? Does anyone know?
Thanks for any insight.