So I'll put my .02 in here.
Example: 100 shots each deal 10,000 damage
skill crits increase that damage 100% but only 50% of the time.
10,000 damage * 50 non critical shots = 500,000 damage +20.5% for break = 602,500
20,000 damage skill critical * 50 critical shots = 1,000,000 damage +20.5% for break = 1,205,000
1,807,500 Total Damage for 100 shots fired.
Now we remove break but us focus instead
skill crits increase that damage 100% but 70% of the time.
10,000 damage * 30 non critical shots = 300,000 damage
20,000 damage skill critical * 70 critical shots = 1,400,000 damage
1,400,000 Total Damage for 100 shots fired.
Now we increase skill critical chance using break enchanting
skill crits increase that damage 100% but 70% of the time.
10,000 damage * 30 non critical shots = 300,000 damage +20.5% for break = 361,500
20,000 damage skill critical * 70 critical shots = 1,400,000 damage +20.5% for break = 1,687,000
2,048,500 Total Damage for 100 shots fired.
These formulas are not 100% accurate and rates may be exaggerated slightly but they give you a pretty good picture of it.
P.S. Keep in mind this takes no other modifiers into account. Base test only.