Check your convergence settings. When my gunnery is on I can saw the wing off a 109 from an F4U-1A with a single tap of the trigger.
That said, I WOULD love to see actual ammunition belt options sort of like ClOD, being able to change the mix as appropriate (IE, tracers in only one pair of guns, tracers by individual aircraft, API vs mixed ball/incendiary etc). Make it part of the Perk system, IE all-API in US aircraft would cost X perks, non-refundable.