The 1st thing is........what model Beretta is it? Their O/U' s can be had in right or left handed versions. The autos such as the 390 and 391 series come with a set of shims for changing the cast of the stock.

The term you are looking for is " cast" . Simply put, it' s the amount(measured in fractions of an inch) the stock is set to the right or left in relation to the rib/barrel.
Actually there are 4 different types of cast on a butt stock but to simplify things we are going to use the " face" . A stock that is angled to the right is " cast off" and if angled to the left it' s " cast on" .

What this does is to put the shooters eye (hopefully dominant) in line with the rib. It also helps with reducing recoil, it should go away from your face. It does make a difference in " gun fit"

You ask if it matters? Picture this......... If you are right handed and are shooting a gun that' s stock is made for a leftie..it' s cast on, not only does it make it hard to have your head in the correct position it also drives the recoil into your face....not good![&:]

But do not fear most typical guns like the mooseburgs, Rem 1100, 1187,870' s have neutral/no cast.


Hope this helps...........AA