The Human Body was never designed with the Twisty Stick in mind, in WWI Sims ANYWAY
In WWII Aircraft, there was some use of Rudder. In Jets even less, except for runway activity

However we're dealing with full travel use in gunnery. That violent momentary course correction just prior to shooting.
It's rather simple actually, I won't say impossible, but it's Very Difficult, to hold a totally flat pivoting action, while squeezing the trigger.
Unless you're Very Careful, you're always going to have a slight Alerion Movement. Just enough to Bank Off Target

I haven't met the pilot, who can hold a turn that flat, without pedals, in a dogfight. I'm sure they exist, but I ain't one.

SOLUTION: Don't use the trigger. Use the Spacebar, your Machine Gun will still Fire, plus your hit percentage will be noticeably higher

Try it and see, and what is your other hand doing then . . in my case I'm on the throttle, but I'm using pedals
HOW TO FIND Your HIT % in OFF . . . Player Stats in Workshop . . On or Off