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I heard that the engineers that worked on the A-10 modified the gun to increase its spread. Supposedly because it was very hard for the pilot to keep the gun perfectly on target, and with higher spread it would still be able to land a hit, even if the plane was aimed slightly off target.

Is this true or just an urban legend? It was hard for me to find a source for this information, except for a single article from aviation geek club, which itself links to a quora article by a self claimed A-10 pilot. The very detailed wikipedia page on the GAU-8 Avenger (the gun used by the A-10) talks about the accuracy of the weapon in detail, but makes no mention of the engineers purposefully increasing the spread.

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    What kind of accuracy would you expect from a 30mm multi-barrelled aircraft-mounted gun? 40' spread at 4000 feet seems fairly accurate to me considering the platform. Commented Jan 23, 2023 at 20:16
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    If this gets closed here (it might, there's 2 votes) you can re-ask on Skeptics. TBH the source is a single self-claimed A10 pilot on quora being cited in your source. So not very promising. Commented Jan 24, 2023 at 2:51
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    It's worth remembering that engineers who work on guns for the military are not paid to make the weapons accurate, they're paid the make the weapons effective. How useful would a hand grenade be that sent all its fragments in one direction?
    – Mark Olson
    Commented Jan 24, 2023 at 13:30

2 Answers 2

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The quote below comes from a comment under the quora article mentioned in the question:

They added, or changed more exactly, the front Muzzle clamp to give the gun an oval pattern to its shots. Each BBL was pointed at a slightly different spot to maximize the chances that at least part of the pattern would be on target!

The commenter who said this studied military avionics and his bio claimed that he has worked for multiple American defense companies, so I feel inclined to believe him. Still, if someone is able to find a more convincing answer that this myth is true feel free to post it as well.

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    So the proposed adaptation is less about reducing weapon accuracy than it is about optimising the spread pattern. Doesn't sound unreasonable. Commented Jan 24, 2023 at 22:49
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    @KillingTime correct. If the weapon is "too accurate" it's actually harder to hit the intended target because the area impacted by the weapon is too small.
    – jwenting
    Commented Jan 31, 2023 at 7:02
  • @jwenting 2/2..., so while I will not say person is lying, it would not be the first someone was making s**t up for publicity (Pierre Sprey, anyone?). Argument from authority is not an argument, and every thing written down contradicts Stewart on his theory, and then there's also physics of flight against him: gun so powerful must fire on axis of the plane and straight, else it will steer the plane instead of pilot, which is a no-no for a close-air support aircraft...
    – AcePL
    Commented Feb 7, 2023 at 8:58
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According to this article (by person observing the development of the GAU-8A) this was not a consideration:

Gun studies were performed with some “what if” ammunition designs, but not much progress could be made in the gun design until the ammunition design was complete. Trade-off studies for the ammunition included not only poking a hole through the top of the tank, but established the accuracy and rate of fire requirements as well. The study was very comprehensive. Each aircraft sortie was designed for a specific number of engagements. On each sortie the aircraft would engage the target for X seconds, at which point Y number of rounds would be fired with accuracy to assure a kill. Hit and kill probabilities were taken into account and the gun rate of fire was established at 4,200 shots per minute. Many believed the system might be more accurate than the calculations indicated. Should that be the case, the gun system would be designed so the rate of fire could be halved, thereby doubling the number of engagements possible on a single sortie.

In other words: the GAU-8A was built to match the specification and main factor in it was lethality (how many rounds to get a kill on target), in turn making accuracy a necessity.

And according to this article the gun's accuracy was very much a factor in selecting the system for the platform:

The GAU-8/A accuracy when installed in the A-10 is rated at 5 miliradans 80 percent meaning that 80 percent of rounds fired will hit within a cone with an angle of five milliradians; this equates to a 40-foot diameter circle at the weapon's design range of 4,000 feet. By comparison, the M61 has an 8-milliradian dispersion.

Which means that gun was selected for superior accuracy. Doing everything that's possible to make it as accurate as possible, and then lower it to get a wider spread pattern sounds implausible at the very least.

In my opinion, spread pattern is inherent to the platform and purpose - 40 feet circle at 4000 feet range is, taking into account recoil of the gun and that it is mounted on a plane, rather impressively small.

I'd put that explanation aside, as literally going against the logic, gun spec and design. But that's not to mention the author of that comment was lying. It may have been what she was taught, it's just it's nowhere else to be found.

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  • Makes sense. Blowing along at 400 mph, you recognize the target, 1 second, orient on it, another second and you've already burned up 400 yards. Not shooting paper targets at the 100 yard range here. A dispersion pattern at a particular range envelop that fits a target parameter is required to increase the likelihood of a kill hit. Therefore, for shooting 5 inch targets, not accurate, but for shooting tanks or the occasional BMP, demonstratively accurate enough.
    – R Leonard
    Commented Feb 12, 2023 at 3:03
  • @RLeonard - True but whatever else, if attacking armor, this is still "spray and pray" kind of attack, because it can't literally be anything else. So at least they tried to stack the odds as much as possible - by just barely stepping down the RPM and with using best ammo available - GAU-8 uses same HEI and API ammo as CIWS and MK44 (latter being used in ground combat vehicles) - but it's hard to not point out that even with that, hit probability is about 10% (1 second burst is about 65 rounds)... I just can't read the question like in OP and not laugh hysterically.
    – AcePL
    Commented Feb 13, 2023 at 8:59

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