That looks excellent Am88...
Id agree with whats been said already...
If you're so inclined, being sensible, go higher--looks like the node isnt far away at all-- give it a try...but personally, id double check around the 18.5 mark...
I only shoot in increments of .3 because from my experience with my gear, its almost impossible to tell the difference in .1 or .2 of a grain diff at 100 with a factory rifle (or the ones i have anyway).
Having said that, none of mine shoot as good as what you have there...
Im not the expert, but if i got that result, id try 2 steps in either .2 or .3 grain increments above & below the 18.5, twice each, but include 18.5 as well...
(In other words...3 shots of 18.1, 18.3, 18.5, 18.7, 18.9--then repeat it again...)
Id also load another 9 (3x3 groups) of the 18.5--shoot one group of that on a clean barrel to start the test, & once finished use another group for any minor scope adjustments...
And even if you dont need them for the testing, you're still gonna shoot out a bunny's pupil & exit out the other at 100...even if you find a better load...
And although it means nothing in comparison to your rifle, my 222 loves the lower end of charges with 2207 as well....
Good stuff going on there...contact me if you want to get rid of that rifle...
Well done...
The man who knows everything, doesnt really know everything...he's just stopped learning...