In answer to several questions, ref. 300S rifles, yes you should 'tip' them after each shot see reply on another thread in this section. Traditional bell target face dimensions are:- centre hole 3/8" dia. then another ring [4] at 1" dia. then another [3] at 2" dia. and the last one [2] at 3" dia. then the last one [0] at 4" dia. the plate is 5" dia. The hole has a military connotation supposedly replicating a mans head at 100 yds. As for front sights, ring elements in metal [with cant bars] or plastic in assorted colours and sizes [ see Andy Lawrence's website for a mind blowing array] are the most common, being theoretically easier for the brain to assimilate a series of circles in line, but some people prefer post or blade elements, this is your personal choice so do not be influenced by others, make your choice and use it.
As a basis for size you have to use a little imagination for this explanation; use trigonometry to get the size of your aiming mark / black dot, at the distance of your front sight of the rifle from the target; put a square frame around this circle; work out the length of the corner to corner diagonal of the square and this is the minimum size of fore sight ring for that target. Having said that, some people will happily shoot bell with a 2mm ring while others use as much as 4.5 mm [ mine is 4mm] the objective is to be able to keep the aiming mark within the fore sight ring, not have a 'now you see it now you don't' scenario, so age, eyesight, ability all have abearing on it.
Hope this helps more than it confuses.
ATVB
abellringer