revolver cylinder gap? sort?

https://preview.redd.it/rjru7yqierbf1.png?width=645&format=png&auto=webp&s=92b57c9b2dee83b2c7d4bc60791a3e66850cd4ae

Is the barrel wider than the bullet diameter at the point where the cylinder meets the barrel?

If the bullet diameter is 9mm, the barrel diameter is 8.8mm. However, if the small part where the cylinder meets the barrel is 8.8mm, there is a risk of explosion.

Is the diameter of the part shown in the photo slightly larger than the bullet diameter? I don't have a revolver, so I don't know.