The Sheridan also had an extremely slow rate of fire due to the naval screw-type breech it had to use in the 152mm main gun. The hull armor would not keep out .50 BMG or .51 Russian machine gun rounds, let alone anything bigger.
The author David Drake rode the Sheridan into battle many times in Vietnam and he had this to say about it:
““The incident around which I plotted “The Butcher’s Bill” was the capture of Snuol the day before I arrived in Cambodia. That was the only significant fighting during the invasion of Cambodia, just as Snuol was the only significant town our forces reached.
G, one of the line troops, entered Snuol first. There was a real street, lined with stucco-faced shops instead of the grass huts on posts in the farming hamlets of the region. The C-100 AntiAircraft Company, a Viet Cong unit, was defending the town with a quartet of fifty-one caliber machine-guns.
A fifty-one cal could put its rounds through an ACAV the long way, and the aluminum hull of a Sheridan wasn’t much more protection.Before G Troop could get out, the concealed guns had destroyed one “of the Allied War Crimes Commission.
The incident around which I plotted “The Butcher’s Bill” was the capture of Snuol the day before I arrived in Cambodia. That was the only significant fighting during the invasion of Cambodia, just as Snuol was the only significant town our forces reached.
G, one of the line troops, entered Snuol first. There was a real street, lined with stucco-faced shops instead of the grass huts on posts in the farming hamlets of the region. The C-100 AntiAircraft Company, a Viet Cong unit, was defending the town with a quartet of fifty-one caliber machine-guns.
A fifty-one cal could put its rounds through an ACAV the long way, and the aluminum hull of a Sheridan wasn’t much more protection.Before G Troop could get out, the concealed guns had destroyed one of either type of vehicle.
The squadron commander responded by sending in H Company, his tanks.
The eleven M48s rolled down the street in line ahead. The first tank slanted its main gun to the right side of the street, the second to the left, and so on. Each tank fired a round of canister or shrapnel into every“structure that slid past the muzzle of its 90mm gun.
On the other side of Snuol, they formed up to go back again. There wasn’t any need to do that.
The VC had opened fire at first. The crews of the M48s didn’t know that, because the noise inside was so loud that the clang of two-ounce bullets hitting the armor was inaudible. Some of the slugs flattened and were there on the fenders to be picked up afterward. The surviving VC fled, leaving their guns behind.”
And from his short story, “The Way We Die”:
““A Sheridan’s bigger than an ACAV but it doesn’t have as much room inside. An ACAV’s just an aluminum box on treads. The TC’s got a cal fifty in his cupola, and there’s two swivel-mounted M60 machine guns for the rest of the crew. With only machine gun ammo and personal gear inside, there’s room enough for all three of the guys who aren’t pulling guard to rack out at the same time.
“Sheridans’re tanks. The hull is aluminum, sure, but it’s got a big steel turret in the middle with a one-five-two millimeter main gun.
“That gun’s the worst thing about a Sheridan, worse ‘n the unarmored belly that nearly rubs the ground. Some bright boy figured out that the brass case holding the gunpowder takes up a lot of room. If you make the case so it burns, you could hold thirty shells in a Sheridan instead of maybe twenty.
“Only the bright boy didn’t figure out what might happen to them thirty bare charges if something started a fire in the turret. If a B-40 hit the hull, for instance, or if you ran over a mine big enough to punch a hole through that little thin floorplate, or if somebody screwed up and set off a grenade inside the hull.
“Ever see a Sheridan burn?
“With all them big shells inside, there’s not room for much else. Our gear goes in the bustle rack, the mesh trough around the back of the turret. Since it’s out in the wet, you can’t just carry your socks in a duffle bag. You either put your gear in empty ammo cans or you might as well leave it back at Quan Loi for all the good it’ll do you in the field.”
““We’d thought maybe the new guy’d want to ride an ACAV instead. There’s six ACAVs and three Sheridan’s in a platoon—full strength; we were already down to five and two—so the platoon leader’s got a choice. Sheridans have the firepower, which is nice; but a lotta guys wouldn’t ride on one for a bet.
“It takes a while to get used to all that bare gunpowder down below you. A lotta things don’t seem important after you been in-country a while, though.”
““Except for the drivers, nobody rides inside a track over here, especially if it’s a Sheridan. And in this troop we don’t fight the main gun except when we’re pulling perimeter security back at the firebase and there’s a dirt berm to keep B-40s outa the hull.
The loader’s got a machine gun welded to the top of the turret. He sits on the hatch cover—some guys have regular seats welded there—and doesn’t have a foot inside the track while we’re moving. The TC, that’s me, has a cal fifty in the cupola. There the red handle to fight the main gun, too, but that’s one shot only: nobody expects the loader to be inside the hull until things’ve quieted down again.”
““When a Sheridan burns there’s nothing you can do but watch. The flames kept roaring out of the hatches for five minutes. The turret settled through the aluminum hull until it rested on the treads.
There were half a dozen smoke grenades inside my cupola. When they cooked off, puffs of red and yellow and violet smoke burped out of the glare.”
Another good summary is here: https://www.quora.com/How-good-was-the-Sheridan-tank
As best I can tell, it was a deathtrap that liked to burn and had a hull that was too weak to actually be used as a tank. It was really a self propelled gun with poor personnel protection,
One of my cousins was a Sheridan driver in a cav unit that was involved in the Cambodian Incursion. The VC/NVA rigged a dud 500 lb bomb into a land mine that went off under his Sheridan. He survived, but carried shrapnel next to his spine for the next 25 years until he died. He told me, when I was enlisting for armor to stay away from Sheridans. I ended up being an Artilleryman in the Fire Direction Center.
A few years after that I became a Recon Sergeant/Forward Observer experimenting with the FIST team concept. I was attached to B/1/32 Armor, 3d. Armd Div as the company’s FO. I had to learn how to fight as a tanker and my tank was an M-60A2 that had the same 152mm Shillelagh gun/launcher. By that time, mid-70s, the 152mm HEAT and Target practice rounds had a combustible casing for the shell, thus there was no brass casing by that time, about 5-6 years after my cousin was wounded in Vietnam.
Father of a good friend growing up was a West Point Armor Branch O-6 (bird colonel) with 2-3 Vietnam tours. This in the mid-70s. He *hated* the Sheridan. There were still some of them around at Fort Knox in that era, more in Germany in the Fulda Gap.