M1 Abrams main gun

[Blakenzy]

How does the 120mm main gun on the Abrams tank retain a high degree of accuracy being that it is has a smooth bore?

 

[Jorg Nysgerrig]

Fin stabilization.

 

[blackguns]

Yep the sabot (AP) has fins molded directly on the round so as the sabots fall away the fins become exposed. Not sure on the other types of round HEAT, SLAP ect.

 

[drgrenthum]

was wondering that myself after seeing a show about sharp shooters yesterday that mentioned the abrams, thanks blakenzy

 

[aka108]

I read someplace that the onboard fire control computer makes adjustments to compensate for barrel wear caused by each firing.

 

[CoRoMo]

How many firings would each barrel expect to see before replacement?

 

[Gungnir]

I think the Smooth bore idea came before APFSDS, since HEAT rounds don't like spinning at all.

APFSDS (Armor Piercing Fin Stabilized Discarding Sabot) can be fired from smooth bore, or rifled, During Operation Desert Storm a British Army Challenger tank achieve the longest range confirmed tank-to-tank kill at 5100 meters or 5.1km with an rifled 120mm APFSDS 'Charm' depleted uranium round.

HEAT works better without any spin on the round and is also fin stabilized. Since spin disperses the Hypersonic jet of superplastic Copper reducing AP effect

SLAP is not fired by a 120mm but a 50mm

STAFF is fin stabilized, and an anti-tank guided munition, that fires a penetrator into the top of the enemy tank (not sure if this is in service yet).

X-ROD (cancelled) Self Propelled guided munition

ERM/TERM Proposed BVR scout/Self guided suspect spin would be bad.

 

[Wheeler44]

Well then, the next question for the pros would be.......
How do the clean the barrels on those guns? I can't imagine that they can clean them from the breech.

 

[waverace]

from the barrel end with a great big cleaning rod and about 4 guys (I s@@@ you not I used to be a tanker )

 

[CoRoMo]

Couple gallons of Hoppes?

 

[Navy_Guns]

Gungnir - there are shaped charge warheads designed for spinning munitions where the liner is fluted to counteract the effects of spin. Not too common, but the exist! They kind of look like a manual juicer dish, if you know what I mean.

 

[amprecon]

I always wondered if a shot was fired down into the loaded barrel of a tank would it set the shell off?

 

[airman]

Weverace is right on for cleaning. I used to be a tanker also. The so called cleaning rod is about 1 1/2" in dia. After you use the cleaning brush, you use a big bell to put towels down to clean it. It was not fun at all!

 

[Caeser2001]

it was no picnic on a paladin either

 

[Pilot]

The main weapon of the M1A1 is the M256 120mm smoothbore cannon, designed by the Rheinmetall Corporation of Germany.

It may be an American tank, but it uses a German gun. The same one as in the German Leopard II.


http://www.fas.org/man/dod-101/sys/land/m1.htm

 

[MTMilitiaman]

I think the Germans, Americans, and British all use basically the same guns and armor. The primary differences are the chassis and the engines. I could be wrong though.

 

[jeff-10]

I think the Germans, Americans, and British all use basically the same guns and armor

I thought the British tank's main gun was rifled.

 

[Kansan]

I spent a few days and nights in Abrams as well and I would rather clean the bore than clean the sub-turret.

 

[Zoogster]

I think the Smooth bore idea came before APFSDS, since HEAT rounds don't like spinning at all.

Actualy smoothbore is used because you can achieve high velocity and with less wear on the barrel. Rifling causes friction.
A lot of resistance and friction and corrosponding increases in pressure are necessary to spin a very high velocity projectile with rifling.

A smoothbore allows maximum velocity with minimum resistance, meaning kinetic energy penetration can be maximized.
It also is unpractical to purely spin stabilize a projectile as long and thin as some of the kinetic penetrators. The required revolutions is insane.
So it just makes better sense to go to fin stabilization.

It is funny that the progression went from smoothbore, to rifling, then back to smoothbore with special rounds.


While not the intended purpose a side benefit of the smoothbore design is the gun can be used as a massive shotgun firing shot in decent patterns. It destroys infantry just like grapeshot once did.
Here is a slow motion video of it in action: http://www.youtube.com/watch?v=Cgn1nhUEgo8
Firing 1150 10 mm tungsten shot projectiles at about 4600 feet per second.

They can also use flechette rounds which pattern even further, and penetrate like crazy zipping through civilian structures.
The most common user of the flechette rounds is probably Israel, who uses them on Palestinians frequently and has therefore generated a lot evidence on thier performance.


There is also rifles now that operate similar to the M1 gun using similar projectile designs:
http://world.guns.ru/sniper/sn46-e.htm

 

[Devon]

I spent a few days and nights in Abrams as well and I would rather clean the bore than clean the sub-turret

I used to walk the line reviewing the -10 2404's looking for something to do. I remember thinking "glad I ain't a tanker", then go get my M88 and have a nap. Cleaning the M3 grease guns and M2 machine gun wasn't so bad after all.

 

[U.S.SFC_RET]

That M1 tank was the biggest gun I ever had the pleasure of shooting. Ahem participating in shooting. I was the loader. That heat round was heavy for me at 220 lbs and strapping 6 foot tall. That means you have to train into that position. We knocked down the sign the target was on. Missed.

Smoothbore gun and big boom.

 

[kentucky bucky]

Didn't the Germans develope the smooth bore that we currently use?

 

[waverace]

to answer a previous query , yes the British gun is rifled ive shot it in both the chieftain and challenger MBT's (main battle tanks) Iwas in the Brit army so only got a one time look see in an M1 , awesome machine much neater than ours with a way better engine , I believe the guns are about the same as far as accuracy goes , you can hit a target the size of a car from 2 miles away even on the move , although thats a little trickier , and we fire the APFSDS (armour piercing fin stabilised discarding sabot) through the rifled barrels too , anybody thats played darts will realise that a spin makes no difference .
I forget now the velocity that those things go but its damn fast like 1500 fps fast , not bad for something that weighs probably close to 60 lbs

 

[frogomatic]

Here is a slow motion video of it in action: http://www.youtube.com/watch?v=Cgn1nhUEgo8
Firing 1150 10 mm tungsten shot projectiles at about 4600 feet per second.

great gobs of goose poop! I like it, but it might be a bit much for HD...

 

[Zoogster]

I forget now the velocity that those things go but its damn fast like 1500 fps fast , not bad for something that weighs probably close to 60 lbs

That is meters per second, over 3x FPS.

Many are over 6,000 FPS.

through the rifled barrels too , anybody thats played darts will realise that a spin makes no difference .

Those designed for the rifling cannot be pushed to the same limits because of the increase resistance in the bore. They would generate far higher pressure propelling the same payload to the same velocity while fighting the resistance of the rifling.
As a result the kinetic penetration suffers.