We established in previous threads that an RPG is pretty much useless against an M1 Abrams tank and even the legendary GAU-8 gun while effective against softer targets would have a hard time killing a M1.
But how would the AC-130 fare against an M1? Would the 40mm Bofors canon be enough to kill it or it will barely scratch the paint? How about the 105mm howitzer?
Well, first of all I would be surprised if the AC-130 routinely carried armor piercing rounds of any sort. The Bofors, even shooting AP, has a much lower muzzle velocity than a GAU-8 and would be significantly less effective. The 105 could conceivably fire HEAT shells, if they exist for that particular gun. A top or rear hit from a HEAT shell would probably kill any main battle tank. Though I would be surprised if a short-barreled howitzer, fired from a plane at long ranges, could reliably hit a tank.
The Air Force uses the A-10 as its anti-tank weapon. The AC-130 is really designed for softer targets, like buildings and light vehicles.
There are HEAT projectiles (the M662) for the 105mm howitizer but they are not fired from the AC-130s. Note that 105mm for the AC-130 use a different cartridge case/propelling charge combination and different fuzes from the howitzer and tank gun ammunition. Hit the tank? On the move, probably not. Stationary, the gun and aiming components are very accurate, I would say first round hit probability would be pretty good. The penetration capability of the HEAT round is classified. With a shaped charge cone diameter of around 80mm, odds are good for penetration of the turret top, ammunition storage compartments and engine deck.
The 40mm should do a mobility kill on the engine from above. There is an AP round (M81A1) that’s an antique but again, it’s not fired from the AC-130.
There has been some interest in mounting the 30mm GAU-8 in an AC-130. The feed mechanism would be modified (turned 90 deg.) but actual space isn’t a problem. It would replace both the 20mm and 40mm guns. The 25mm chain gun from the Bradley/Marine Corps LAV has been tried but not adopted.
Wouldn’t the 25mm GAU-12 gatling gun be enough for a top kill on an Abrams? ISTR that the 25mm rounds will penetrate 69 mm of RHA, and it’s pretty doubtful that a tank would have almost 3 inches of armor on top.
Except that the Abrams (or any modern tank, really) doesn’t use rolled homogenous armor. Instead it uses a composite. For comparison, it’s frontal armor is considered to be equivalent to somewhere between 52 and 64 inches of RHA. It’s pretty heavily armored, true, but it definitely doesn’t have a five foot thick slab of steel bolted to the front. I would hazard a guess that the M1’s top armor is better than 69 mm RHA equivalent.
Plus, the 69 mm RHA penetration figure for a 25mm round is in the best case: short range, direct hit. Fired from an AC-130, the 25mm round would travel a long distance and lose a significant fraction of its speed. Plus, it would hit at a sharp angle, perhaps around 30 degrees. All of that reduces the round’s effectiveness considerably.
Sure they do, but just not in places they’re likely to be hit by tank guns or antitank weapons, like the top.
Just how high do you think AC130s fly in combat anyway? 500-2000 metes (roughly 1500-6000 feet is what I’ve been able to find as the standard combat altitudes.
Spot on. 105mm is far heavier of a weapon class than the M1’s top was intended to proof against, and since HEAT’s penetration is chemically derived, any difference in shell velocity due to aircraft delivery is irrelevant to the effect on target. The M1 would likely not survive a solid hit.
That said, this is a theoretical matchup. Aside from the practicality of equipping AC130s with HEAT rounds, which diminishes the effectiveness of their intended role, in a Fulda Gap sort of scenario, armor concentrations would always have short-range air defense readily available and the AC-130 is a big, slow, soft, and ungainly target. Due to the extreme lethality of close air defense threats, air to ground attacks specialize in one or more of four core profiles: very low altitude, very high altitude, high speed or standoff ranged. The AC-130 can’t fit well into any of those niches and would be a poor choice to send against armor.
Actual penetration figures for the latest 25mm AP round, XM/M919 DU, are classified. The M1A1 top armor RHA equivalence is also classified so we are just guessing. The angle of impact would be much more direct. The AC-130 is usually banked pretty good when engaging targets. Darn near straight down from the guns perspective; let’s say >60 deg.
I saw evidence of an earlier non-DU AP round of 25mm, the M791, penetrate the side of a T-54/55 turret in the aftermath of Desert Storm. That’s cast armor but still fairly thick. I have a shoe box of 1200 pictures/negatives I’ve been meaning to scan in for the past almost 20 years (got to get to it soon:eek:). One of which shows the impact, penetration, and resultant destruction.
I wasn’t assuming really extreme ranges, my intuition was a few thousand feet high, with a few thousand foot “orbit”.
(FWIW I tried googling more details on penetration, and I think the 69 mm penetration you’re recalling is for the GAU-8 at 500 meters. At 1000 meters, it’s reduced to 38 mm)
Again, my point stands that at longer ranges (1000 meters? 2000 meters?) and greater angles (30 degrees plus or minus) the penetration will be greatly reduced. At 30 degrees, the armor is effectively twice as thick, and there’s a chance that the incoming round is deflected.
Fair enough. 60 degrees would surprise me (could a plane that big maintain lift with that much bank?), though 30 seems like a very conservative estimate on my part.
That’s reasonable, but I’d bet that we’re looking at somethings less than 50mm of armor on top (a full 2"!) We’re probably more in the ballpark of 20-40 mm.
AC-130 fire cone angles are ballpark 45 deg, not 60. The aircraft is ~30 degres of bank & the gun is depressed ~15 below that. Been there, done that. If the bad guys have any small arms, we’re gonna want to be above 5K, maybe as high as 10K ft above the target. That translates into slant ranges of 12-15K ft.
Typical AC-130 105 loads (HE) won’t penentrate any meaningful armor. Certainly not the top of an M1. You could fire HEAT, but as noted above it’s not normally done.
The last time I was overseeing shooting from an AC-130 was the mid-1980s. In those days the CEP of the 105 was such that hitting a single tank in a big empty field was luck, not skill. With any AP-type round, a miss by 1" is a dead miss with zero combat effectiveness. Not like an HE round against soft targets where damage is mor or less proportional to miss distance.
That was AC-130E models. Maybe accuracy is better with the AC-130Us. But my bet is not enough to matter for this scenario. The tank will not hold still long enough for the AC-130U to refine it’s aim throughthe 2 or 3 shots necessary to hit a tank-sized target. These things are not death rays, no matter how much Military Channel you watch.
As well, as somebody upthread said, bad guys don’t deploy massed armor without massed air superiority & massed anti-air defense. Lacking either of those things they’re simply destroyed in detail by US TacAir. But *with *either of those things, the combat lifespan of an AC-130 in that environment is measured in seconds, not minutes.
I could imagine a scenario where some rebel or irregular forces have a tank or two but no meaningful air defense and the good guys have an A-130 or two. If they ever met, they’d be mutually ineffective. Entertaining to watch, but indecisive.
In any case, from what I understand, the more likely strategy, assuming that both vehicles were not operating in a vacuum, would be for the AC-130 to designate the target for someone else to kill, such as a nearby attack helicopter with Hellfire missiles. The other guy wouldn’t even have to see the target, he could lob the missile up over the other side of a mountain and it could find its way from there.
Of course, the other guy wasn’t part of the OP’s premise.
EDIT: Oh, and obviously, if both planes were operating in a vacuum, the tank’s engines wouldn’t work, and the plane wouldn’t be able to fly. 
Tanks are more vulnerable than many people think.
Things like sights and sensors, which are needed for a tank to perform well in modern warfare, are usually protected against heavy machinegun fire and nothing heavier.
Whether a GAU-8 would kill an M1 or not, I don’t know. But I’m pretty sure it could leave it blind and useless.
And also, artillery can kill tanks. A direct hit from a 105mm shell imparts enough shock to be able to break things. Yes, you’re unlikely to one shot kill a tank with a 105mm HE shell, but you could quickly leave the tank uselss.
I’m told that the modern M-1 is qualitatively different. In one of the recent wars, American tanks tried to destroy M-1s that had to be abandoned, and found that depleted uranium penetrators fired at point-blank range often totally failed to go through the enhanced armor – and they were aiming for “vulnerable” spots. They’re not invincible, but they’re orders of magnitude stronger than previous generations of tanks.
If you want to kill a disabled tank using DU AP, you’d fire into the rear armour. The armour is substantially thinner there.
I seriously doubt 105mm artillery shells could put a hole through M1 armour. I doubt heavier 155mm shells could put a hole through the M1s armour either. But with HE you’re not trying to penetrate the tank. You’re trying to break things using shockwaves.
I bow to your first hand knowledge.
I never flew on one but did review dozens of mission tapes. From some of the camera angles, it seemed like they were pivoting in a very tight cone around the target(s). The camera angle (spooky night-vision green) may have been steeper than the aircraft of course.
The crews I associated with would “zero” on the way into country on a known badly destroyed settlement at the altitude the mission was expected to operate at (“no plan survives first contact” caveat). The 105 guys felt they could get first round hits on a 12’x12’ building 50% of the time so I suspect the aiming and ammunition has tightened up considerably. I saw a number of hits on individual buildings in small compounds with no surrounding craters.
I did my viewing recreationally 
after doing my ammo wizzardry so my sampling might have included a lot of, “best of our missions…”, examples. I’d be cooked from the heat so I’d go in HQ/tent/pole barn and watch while recovering.
I think both an RPG as well as a GAU-8 have a decent (call it “better-than-even odds”) chance of scoring a mobility kill on an Abrams.
Remember, the easiest way to kill a tank is NOT to penetrate its armor, but to kill/disable the squishy organic bits inside. A 105mm HE may not penetrate the top armor, but I personally would NOT want to be inside any tank taking such a hit.
If the Abrams was in typical “open hatch” travel configuration, would the fire density of a Puff be enough to get a few rounds inside the turret through an open hatch and shred said squishy organic bits?
Let me rephrase:
“Killing” a tank isn’t always about blowing holes in its armor. Taking out the crew, while not easy, is also a viable option.
ExTank, from your experience, could an Abrams successfully engage an AC-130 with either the commander’s .50 or the main gun? I’d think the 5000 foot + orbit altitude would make the COAX ineffective.
I’ve spoken with tankers who claimed, if they had no other choice, their countermeasure to a helicopter engaging with ATGMs was to try and kill it with the main gun (M-48A5’s 105-mm). They seemed confident they could do it. Of course, hitting a hovering Hind near the ground is probably a LOT easier than trying to see/track an AC-130 at night. (Could you even see it, even with NVG? I’m guessing the Thermal Viewer could pick it up, provided the AC-130 was within the F-o-V) Still, sabot rounds have sufficient range to hit the AC-130. And the ungodly muzzle velocity would make the lead calculations a little easier.
Can the Abrams’s main gun even be fired while the turret was traversing, like a wingshooter swinging through the bird? Or would you just put the sights “X” plane lengths ahead, and then shoot?
