...Barrels don't get stiffer when material is removed from them, no matter the final shape they are machined to. The stiffness of a barrel is a result of the "quantity" of steel used, not the finished shape. Unless the triangular barrel provides a dimension that incorporates more steel, it will not be stiffer than a barrel of round configuration incorporating a like quantity of steel. ...
Actually, it is not the amount of steel that is the primary determinant of stiffness but the distance from the centerline to the outer edge. The reason a fluted barrel is stiffer than a non-fluted barrel of like weight is the fluted barrel is larger in diameter.
Since a triangular barrel can have a greater distance from the centerline to the extreme edges, it may well do a better job of providing greater stiffness for a given weight. Whether the difference is better than a round, fluted barrel remains to be seen.
