To give you an idea of the cooking capacity of the Weber Bullet without any modifications, I have cooked the following quantities of meat at one time in my cookers. (Not the entire bulleted list at one time, just each line!)
Comparing Capacity Between 18-1/2" and 22-1/2" WSMs
Here are some photos showing how much meat you can fit in the 18-1/2" WSM versus the 22-1/2" WSM. Click any of the photos to view a larger image.
Beer Can Chickens
In the 18-1/2" WSM, the chickens touch the underside of the top cooking grate—they do not in the 22-1/2" WSM. Notice that I squeezed 5 beer can chickens onto the bottom grate of the 22-1/2" cooker.
Baby Back Ribs
Three slabs of ribs can lay perfectly straight in the 22-1/2" WSM, and it can easily hold 6 slabs of rolled ribs on the top grate.
Three boneless pork butts on the top grate of the 18-1/2" WSM; 4 on the 22-1/2" cooker.
These photos show the same 15.39 pound whole packer brisket on the top grate of each cooker. This brisket could be cooked in the 18-1/2" WSM by "shoehorning" it between the grate handles and it would shrink during cooking, but a 12 pound brisket would be a more comfortable fit.
Increasing Cooking Capacity
No matter how big your cooker, there are always times when you wished it was just a little bit bigger! See Increasing Cooking Capacity for ideas on how to fit more barbecue into your WSM.