Like others, I think in thousandths. But that often elicits the deer-in-the-headlights look from people less knowledgeable than those who post here. So I often find myself using the "nominal" terms of SK, IC, etc. and explaining how to equate the two conventions....which is what these cahrts attempt to do.
AND, in that regard, I don't like ANY of the posted charts.
I find it much easier to simply think in terms of 5 thou increments for a 12ga, which covers 90% of the choke conversations I have.
.005 = SK
.010 = IC
.015 = LM
.020 = MOD
etc.
I can recite those in my sleep.
Likewise, I like a nice round .025 for full in the 16/20ga, .020 for IMOD, .015 for MOD. I mean, c'mon, who thinks the 16ga and 20ga should be .001" apart? and that .019 and .014 are better estimates than .020 and .015?
