Ballistic Products has published some 1.5 ounce buckshot loads using Longshot powder. Two with what they are calling the Fiocchi 616 Magnum primer and one with the Fiocchi 616 Standard primer. There is a substantial difference between the flattened spherical powder charges shown with these two primers.
Indeed, this Load of the Week data includes this description of how Longshot powder responds to the new Magnum primer in these loads:
"Longshot has shown a very volatile change, which could be traced to Longshot’s ignition qualities."
These can be viewed at:
https://www.ballisticproducts.com/load01152021.htm