watching the flash

or over gripping the wrist pulling to the right . try from a good solid support and see if his groups tighten up then adjust sights to center and than off hand. aim at a small bright spot.
try having a 2nd person load prime the pan /not prime and watch for a flinch. the shooter never knowing if it's primed
develop a shooting rhythm
proper breathing , deep breath in and out then let part out hold
a line sights don't death grip the stock
slow squeeze trigger , surprise shot/hammer fall ignore the flash (when you can see the patch fly down range you are no longer watching the Flash, hold on target till hearing the ball hit(fallow through)
don't rush the shot, if your rhythm is interrupted start over, you don't have to shoot
unless it feels right( in archery we call it TARGET PANIC) the feeling that you have to shoot even if it's not right