Thread: Advice needed

30mm is typically more rigid and the turrets and adjustments can be made tougher all things being equal - traditionally the diameters were 1" (25.4mm) and 26mm for the Euro types. No real difference on a zero'd rifle where you are "point blank" shooting (i.e. one you are just lining up the crosshairs on anything from 0m out to 300m).

30mm will likely be heavier but where the bigger diameter is better is for dialling scopes, wider at the adjustment turrets allows a longer thread on the adjusters which = greater adjustment for range. The trade off is bulkier heavier mountings, but all things being equal on a poo70 you won't notice much between the two sizes all other characteristics being equal.

More relevant issues for me would be the position of the scope for correct eye relief (clearance forward and rearward), height over the action (clearing everything it needs to while being in line with your natural eye position and then clearing everything on the front of the rifle like rear sight bases and suppressor etc etc.