The Mag Spark might play a small part in it but how your load is put together probably has much more to do with it.

How is your load constructed and what is it made up of?

Whether your shotgun only has a cylinder choke or not, you need to use a plastic shot wad along with placing some wadding under and over it.
Heavily compressing a ball of newspaper under the plastic wad and lightly compressing another smaller ball of newspaper over the shot load has worked for me, as well as using plastic shot wads which help to keep the shot load together longer so that the pattern will be tighter.

If you can't get it to pattern with 100 -120 grains of shot by volume and 90 - 100 grains of powder, then maybe you need to shorten the distance and adjust your point of aim.

Some folks wrap their shot load inside of a type of paper cartridge and experiment with cutting a few small slits of varying lengths in it. But using modern plastic wads are much easier to use and produce more consistent patterns.