Well I wasn't relating so much an impossibility of doing damage with character scale weapons to either speeder scale or even walker scale structures, but the important consideration is damage scales are dealing with structure. The golden-bb would be considered a plot point, where an amazingly lucky shot penetrated a relatively weak grille to cause catastrophic damage to a heat exchanger...in mundane combat it still relates to the general guideline it would take (according to damage scales in RPG) around 30 troops concentrating fire with hand blasters to guarantee that one lucky shot within a 6-second combat round of choice.
And let us consider the historical role of the golden-bb (an American term), during the fighting for Stalingrad General Chuikov said that ordering troops to use infantry weaponry, even support weaponry like anti-tank rifles being mounted to makeshift tripods for use as light-AAA, was wholly a device for morale. Stuka are virtually immune to ground fire in the dive, prior to the dive they are several kilometres away (at 2-3km altitude) and following the dive execute a zoom recovery which is equally hard to track/lead, the best opportunity is a small window as stuka level out and return home slowly, at low altitude of 500-1000m about a kilometre from the target. It's not a big window for infantry weapons (but they are extremely vulnerable at this time for 25mm and larger AAA).
Consider that dedicated fighter-bombers were routinely armoured against rifle calibre groundfire from 1940, and by late 1940 many of these features were incorporated into standard fighter models. A P-40 could be taken down by massed rifle fire much easier than a P-40B for example (or a BF-109E-3 compared to an BF-109E-4). The notable exception would be Japanese fighters and attack models.
By midwar the preferred, dedicated fighter-bombers not only included heavy armouring, particularly around the oil cooler but tended towards radial engines (Fw-190A/F/G, La-5), which increased survivability against even medium calibre ground fire. It is a very lucky shot indeed which can bring down an Fw-190F with a rifle calibre, there are very few places for it to hit which are going to do any appreciable damage or threaten the pilot (the floor, seat, walls and cockpit glass being all armoured, as well as engine cowling, reduction gear, hydraulic/oil piping, ammunition cases, aircraft underside and the controls are electrical w/backups, and there is no water-radiator to hit).
Here's where we get the pilot folklore of the golden-bb. During 1944-45 Allied strafing missions were more common than air superiority ones, and many regular fighters were adapted as fighter-bombers. Aircraft with vulnerable radiators and relatively little specialised armouring, like the Spit FB variants and P-51's. They did their job well, but gained a reputation for being downed by lucky rifle calibre groundfire. According to USAAF testament the Mustang "could be taken down by a single rifle round in the right place" (the reason the P-47 was the preferred fighter-bomber even though its low altitude performance without ADI water-injection was sluggish at best). The Spitfire FB variants also had this reputation.
To properly armour a water-cooled attack a/c from groundfire you wind up with something like an IL-2 Sturmovik (nicknamed the flying tank), which has a basic single seat fighter layout but is virtually immune to small and medium calibre groundfire (designed to shrug off anything smaller than a pom-pom). Gunther Rall said the only way to take one down using his 1x 20mm and 2x 7.92mm in an Me-109F/G was to sit on its tail at close range for extended periods and slowly break away its control surfaces. The Sturmovik (its cockpit/engine area encased in a thick, stainless steel armoured bathtub not unlike the titanium ones of the modern A-10 and Su-25), was so heavy that even with an engine roughly as powerful as an early Griffon it is a slow and sluggish beast to fly. Nevertheless you simply couldn't take one down without extreme patience and once they redesigned it with an armoured rear-gunner armed with two 12.7mm machine guns the IL-2 actually started accounting for many air-air victories defensively.
Things changed dramatically in the jet age and the golden-bb gained its most fearsome reputation in Vietnam, where more than 50% of all F-105 Thunderchief fighter-bombers were shot down by groundfire, and a notable proportion of these, plus a few Phantoms were taken by massed rifle fire from overflown encampments at hilltops and the like.
Jets are however a different matter and aren't armoured anything like the fighters of WW2. An F/A-18 Hornet can most definitely be taken down with a good rifle, but the problem is you never see one even when being attacked by it. By use of effective tactics such as wild weasel operations, AWACS and triservice/international mission support regimes, the first you'll hear of a Hornet is the sonic boom as it flies somewhere out of range and out of sight, then a few moments later the entire area will be laid to waste by its independently targeting ordnance.
If the blighter would just fly past nice and close at a comfy 400km/h level speed yeah you could take it down with a .30/30 (a .50 BMG would be better).