Try going on Shotgun World, those guys may be able to help.

I am confused......you say you have "the" Briley choke...which one???

If it's not marked "Diffusion" and is not rifled it's not a spreader choke made by them. Briley makes an extensive line of chokes for just about any make of shotgun.

Try calling the number I listed above and see if they can explain it to you in your language.

Briley+Diffusion= spreader choke, it will throw a 30" inch pattern at 10 yards

Like this big

Briley+Diffusion= spreader choke, ok but it is not seminole spreader choke. I have diffusion choke and it is good but it is only for short distance.