The best way to know if your gun has this tendency is to shoot 2 shots at the range, 1 clean, next fouled. that will tell you if you have a change in point of impact (as well as point of aim)enough to justify fouling first. This is also a good idea to do so you know if a quick follow up shot is going to go where you want it to.

I have some loads that need a fouling shot and others that don't. If your close to point of aim on a clean barrel at the range you expect to shoot, don't worry to much about it.

Good luck.