Barrel port size

[angrybear]

Can anyone tell me the barrel port size for .25 FAC, both FF & reg, as I assume the reg'd port is larger.

I'm toying with trying a reg on mine as I've got one in the cupboard, I've also got a spare .25 cal 23.75" barrel with a 4.8mm port,
It's just to save disturbing my current FF barrel if I don't need to, as I know how well it shoots.
ta.

[jackrooz]

I'm pretty sure my .25 is 5mm with stepped oval porting and I'm regged