Sheridan: the worst armored vehicle to see Army service:

[Matt Wiser]

The Stingray's late and unlamented predecessor, the M-551 Sheridan:


The M-551 Sheridan in World War III


The M-551 Sheridan armored reconnaissance and airborne assault vehicle, a light tank for all intents and purposes, was one of the lesser-known armored vehicles to serve in the Third World War. Replaced by 1985 in armored cavalry units by tanks and either the M-113 ACAV or the M-3 version of the Bradley fighting vehicle, the Sheridan was still in active service in the 3-73 Armor (Airborne) of the 82nd Airborne Division, and only for its air-droppable capability, while other examples were serving as OPFOR (Opposing Forces) vehicles at the National Traning Center at Fort Irwin, CA. Most other vehicles were in storage when the war began, and were rapidly issued to both newly forming units and Army National Guard formations. The Sheridan was not popular among its crews, and earned the nickname “Purple Heart Boxes” for their tendency to explode and burn after being hit by enemy fire. With their magnesium armor, they burned brightly, as their crews found out to their horror. Armed with a 152-mm gun/missile launcher, which could also fire the MGM-51 Shillelagh missile, the Sheridan was not able to tackle the latest Soviet armor, such as the T-64, T-72, or T-80, but was able to deal with Soviet APCs and the earlier T-54/55 series of tanks, as well as the T-62.

Several attempts to update the vehicle were made, with either 76-mm, 90-mm, and even 105-mm guns, but none were proceeded with, and it was finally replaced in U.S. Army service during the war by the Cadillac-Gage Stingray, and after the war by the M-8 Buford Armored Gun System.


Versions:

M-551: Initial production version used in Vietnam, upgraded with ACAV gun shields for the commander's .50 Caliber machine gun and underside armor.

“Two box” M-551: Version with missile guidance equipment removed, and missiles removed to make room for additional main gun rounds, and extra 7.62-mm and .50 Caliber ammunition.

M-551A1: Upgraded M-551 with laser rangefinder.

M-551TTS: M-551 with Tank Thermal Sight.


Users:

The United States Army was the only user of the Sheridan. The vehicle saw service in both Northern and Southern Theaters, and saw its last combat in the Brownsville Pocket in 1989 with the 82nd Airborne Division. The 82nd was the last user of the Sheridan, though it saw limited service with the 11th Airborne Division in the Southwest.

[Wolfman]

Calling the Sheridan a dog is an insult to dogs. The only thing it was good for was OPFOR duties at the NTC (and even they dumped it postwar in favor of the genuine article)…

[Poohbah]

Worst incident we had during the Los Angeles mess was when a National Guard Sheridan (newly issued) took an RPG in Boyle Heights and the armor caught fire. Vehicle melted into a puddle of molten metal right there in less than two minutes. The crew didn't get out, and I don't think Graves Registration ever recovered enough remains to have proper funerals.

[Bernard Woolley]

What idiot decided to issue those poor Guardsmen with the M551? Tantamount to murder, IMVHO.

[Poohbah]

What idiot decided to issue those poor Guardsmen with the M551? Tantamount to murder, IMVHO.

Sierra Army Depot had a bunch on hand, 1-18 Cav needed SOMETHING immediately if not sooner because LA had gone up in flames, their armory was in enemy hands, and nobody quite realized how bad the magnesium armor was against the latest RPGs.

At least Sierra Army Depot bolted bar armor onto the vehicles before issuing them. They tried to do right, but it just wasn't enough.

The Sheridan would burn if hit and penetrated by a 'Nam-era RPG-7 (the damn interior was a bonfire waiting for a match; one undocumented feature about the 152mm ammo is that the casing was combustible and would deflagrate from hot splinters or spall), but the PG-7VR round fielded in the early 1980s had enough thermal energy to push the point of penetration well above ignition temperature, even if it hit the slats on the bar armor (the big 110/125mm HEAT rounds, or any full-bore ATGM, would also do likewise). The description I got was that the edges of the penetration would start burning, and within about twenty seconds the entire hull armor package (the turret was steel RHA, thank God) would be fully engaged. Once the armor was burning, that was it; you couldn't extinguish it in the field. If the crew wasn't out within five seconds, that was generally that, because the ammo would be on fire by then.

It didn't help that the M551 wasn't especially well-engineered for facilitating egress in the event of, "Oh bugger, the tank is on fire." Better than WARPAC tanks, but not by much.