I hate giving a "it depends..." answer, but I have to.
It depends on the the type of action (pump, single, semi-auto), and the material you have to work with.
A handgun designed for .38Special may not be strong enough for the .357 Magnum, even if you can lengthen the chambers.
In otherwords, I would not recommend it as the 3" may develop greater chamber pressures than the 2 3/4".
"A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed."
Life Member NRA
Life Member NAHC
Former President of the ECPT (Eifel Combat Pistol Team)