And if you're shooting sabots, you really should be using a rifled barrel.
And, BTW, I have chronographed many slug and buckshot loads before I retired from LE.
My results were very different from yours.
I didn't fight to defend your freedom so you could vote to take away mine.
"A man who has nothing for which he is willing to fight, nothing which is more important than his own personal safety, is a miserable creature and has no chance of being free unless made and kept so by the exertions of better men than himself.
John Stuart Mill."