when it comes to firearms, there are very few stupid questions....
The most common c-o-c action (in Aus) is the Lee Enfield based rifle, mostly 303Brit, but there are 25, 27, 30 cal examples throughout... dont know if there are 22 cal versions in centrefire... no doubt it has been done.. it has been necked up as well but I dont know about 50cal.
Pros and cons, I like the feel of the compressing of the fire\ing pin as closed, but most have never handled or operate such a rifle, others include the older mausers, swedes, etc NOT the 98s which are cock on open.
Cock-on-open require the lifting and camming of the bolt (after discharge - ejection) to compress the firing pin and (obviously) cock the mechanism so the the stripping of another round from the mag and closing of the bolt has only the resistance of the round entering the chamber and bolt lugs engaging.
Some prefer the feel of the c-o-o, some prefer the more linear compression of the firing pin spring on closing....
Cock on closing removes the cocking resistance from the extraction of the round after lifting the bolt - so that the lifting and rearward movement of the bolt after firing only disengages the lugs, extracts and ejects the round.
I'm unaware of any current production rifles with c-o-c... maybe there are some old-schoolers out there.
c-o-c examples include the Lee Enfield family, the Pattern 14 303 / m1917 30-06, all pre98 mausrs...
c-o-o examples include m98 mausers and all current production bolt actions...