PJ,
I don't shoot steel. I have about 40 rounds of Heavi-Shot that was purchased a while back, and have used 2, thus far.
Mostly, I stay out of areas that require non-tox. This is the first time in about 10 years I have been on Sherburn. It is less than an hour away, and was just a good armed hike, today. The bird was a bonus.
The chokes on the Nitro are cylinder, and modified, by the way.

Best,
Ted