Tank barrels

[twodko]

I've always been curious about the "hump" on a battle tank's barrel.
What is it and what does it do?

[herccheif]

It's a fume extractor. Basically prevents all the gas from blowing back into the turret when the breach is opened. If you watch a video of one fire you'll see it in action. There is the initial burst of gas and flame and then a smaller puff.

[lazyworm]

not sure if there are more than 1 type. The one I heard of is basically an air chamber. When the cannon fires, compressed gases is trapped in there, after the round left the barrel, the compressed gases blow out of the front of the barrel and suck all the smoke out from the breach. That's why you sometimes see a puff of smoke come out of the barrel shortly after the round is fired.

[Zamble]

It's called a bore evacuator. And it works great. My tank commander and gunner didn't re-install ours properly and our whole tank filled with smoke from the main gun. Learned the lesson of checking on those two's maintenance after they were done after that.

[skosh69]

It's called a bore evacuator. And it works great. My tank commander and gunner didn't re-install ours properly and our whole tank filled with smoke from the main gun. Learned the lesson of checking on those two's maintenance after they were done after that.

Bingo ^^^

Question, how did they not re-install it properly? They forget a gasket? Not tighten the lock ring properly? Only issues I ever encountered with the barrel was when we'd get a new bore brush. God that sucked. It'd take damn near the whole platoon to punch a gun tube. Those were the days.

Also OP, by looking at the size of the bore evacuator, you can tell the size of the main gun. The 120 MM has a more pronounced "hump" than that of the 105 MM barrels.

[Zamble]

Yeah, the locking ring was installed all the way. My TC and gunner were basically known as dumb and dumber. TC was battalion photographer and the gunner was our CO clerk. I had a winning crew.

[DesertDave100]

I've always been curious about the "hump" on a battle tank's barrel.
What is it and what does it do?

I have only a few questions left on my list, now that I know the answer to this one. Thanks for asking! I didn't realize how often I'd wondered the same thing.

[Fastattack]

I didn't know that - all this time I thought it was a resonance dampner.
Thanks for the info.

[Zamble]

But I will never forgot the smell of shooting a main gun and coax. I miss that.

[BigBronco]

Thanks I wondered about that also.

[Sentenza]

But I will never forgot the smell of shooting a main gun and coax. I miss that.

For a short while, my entire crew were Cali natives. We painted a Fan Palm on the turret.

Those were the days.....

[skosh69]

But I will never forgot the smell of shooting a main gun and coax. I miss that.

Ah yes, nothing like it.

Funny thing that your head is riding right next to the breechblock, yet you really don't hear a thing but the the afcap dropping to the turret floor or the spent brass collecting in the coax chute.

I would pull each and every tracer round from the beginning of gunnery and save them for the "widowmaker" on TT VIII. Nothing like a laser show at night. It never failed to draw attention.

Got my *** chewed more than once, but it never stopped me.

D-12 "Deranged and Delirious"

Like Sentenza said, "those were the days".

Thanks for bringing back the memories guys.

Tomorrow, I'll take some pics of the tank crew pics I have hanging in my work station. Been up there 20 yrs. I don't even have pics of my family hanging in my work station.

[skosh69]

Top pic was during Operation Bright Star in Egypt. Lower pic was during a gunnery at Ft. Stewart, Ga.

[hermosabeach]

I learned something new today

I thought it was a 2 part barrel

https://en.wikipedia.org/wiki/Tank_gun

They often display a bulge in the barrel, which is a bore evacuator, or a device on the muzzle, which is a muzzle brake.

https://en.wikipedia.org/wiki/Bore_evacuator

A bore evacuator or fume extractor is a device on the gun barrel of an armoured fighting vehicle which helps prevent poisonous propellant gases from venting back into the vehicle's fighting compartment when the gun breech is opened to load another round. Bore evacuators are most often used on large-calibre tank guns and self-propelled guns. Without bore evacuators, hot gases and other combustion residue leaks into the tank's interior, depleting oxygen levels and filling it with a foul odour that can easily induce nausea and distract the crewmen from their tasks.[1]

Foreground, a close-up of the bore evacuator on an M1 Abrams, while another tank fires in the background
The evacuator is a simple passive device. It consists of a ring of holes drilled into the barrel, surrounded by a cylindrical pressure reservoir. As the shell moves down the barrel during firing, it reaches a point where the base of the shell passes the set of holes. The high-pressure propellant gases in the barrel behind the shell blow into the pressure reservoir through these holes, charging it with gas. As the shell continues down the barrel the pressure begins to drop, and then suddenly returns to near atmospheric pressure as the shell leaves the barrel. During this process the high-pressure gas in the reservoir begins to blow back into the barrel. By aiming these holes forward, their exhaust causes the gases to be blown down and out of the barrel.[2]

[skosh69]

Here is pic of a "butterbar's" tank while I was stationed in Germany.

The story behind the "ripped" barrel is this:

The tank went over a large berm, gunner did not keep the cadillacs engaged and the gun tube was plugged with dirt. Unknowing of the dirt packed gun tube, they fired off a round. I heard they actually managed to get a hit.

The range was shut down and a "police call" was performed of the entire range to find the MRS. IIRC, it took hours upon hours find the MRS.

Look at the tank behind the one with the ripped barrel, what looks like a front sight, is the MRS.

The butterbar was written up for dereliction of duty and I heard had to pay for the gun tube.

Oh yeah, The MRS or muzzle reference system is an electronic device that is intended to measure the current value of a tank barrel bend in order to take it into account when firing the gun and therefore to improve the accuracy of firing.

The electronic signal proportional to the measured angle value is transmitted into the tank's fire control system that allows to indemnify the firing errors by correction of the relevant aiming angles. The measurement error of an up-to-date muzzle reference system does not usually exceed 0.1 mrad. The system consists of a reflector ("mirror") installed at the gun muzzle end and a measuring unit installed on the barrel near the gun mantlet. All modern main battle tanks are fitted with a muzzle reference system.