I coat and bake 14-14.5 lbs of bullets at a time. I'm using an Oster countertop convection oven whose total wattage is 1500 watts. I'm like most ovens and folks, I monitor the air temp in the oven. Could be the total mass I'm trying to heat requires a longer time to get up to temp to cure completely. Kinda like the extra time to bake a 5lb turkey or 3 5lb turkeys at one time in the same oven.