Keep in mind that choke is not so much a matter of thousandths of an inch of constriction as it is a matter of percentage of bore reduction.
.020" in a .410 bore gives the same % of reduction as .035" in a 12 gauge. With more constriction than this is a .410 you were likely encountering an "Overchoke" condition.


Miller/TN
I Didn't Say Everything I Said, Yogi Berra