The short answer is no, airsoft BBs come in various sizes and weights that give players an added level of control over their airsoft setup.
The most common BB sizes are 6mm and 8mm, with 6mm being the most popular.
6mm is most popular because the majority of reputable airsoft gun designers and manufacturers now produce rifles that use barrels around the 6.03 to 6.08mm diameter size. These barrels are known as tightbore barrels and they enable BBs to travel more accurately, faster and further.
This is because the gas that is pushing the BB has less room to escape from around the BB as it travels down the barrel, meaning more of it is acting on the BB and giving it more velocity.
This obviously makes the BB travel further.
Most airsoft rifles, particularly entry-level rifles come with 6.08mm barrels, but it’s becoming more popular to see 6.03mm tight bores installed as standard. It’s even possible for you to customize your barrel and add a 6.01mm barrel if you really want to increase your FPS and max out the performance of your gun.
Obviously, an 8mm BB won’t fit into these barrels and will need a corresponding 8mm barrel which isn’t so common, so this is something to make sure you double-check.