Battle tank barrel "bulge"???

[oldred]

A buddy and I were talking about the tanks the military use today and he asked "what is that bulgy thing about half way on the barrel of their cannon"? I couldn't answer since I don't have a clue but it seems to be on all large tank guns (cannon) and I have in the past wondered the same thing, I am SURE most of you know and so I thought I would ask!

[oneokie]

It is an evacuator. It is designed to evacuate the powder smoke from the barrel and turret, so that the crew cabin does not fill with smoke everytime the breech is opened to load another round.

[Outpost75]

Bore evacuator to keep propellant gases from entering the turret when breech is opened.

[fouronesix]

I think you are referring to a gas evacuator... to keep residual powder gases from venting back into the tank when the breech is opened.

beat to the punch x2 :)

[oldred]

Now I know but I don't know what a "Battkle" tank is!, fumble fingers! :roll:

I didn't even notice that little boo-boo until I came back just now, sure wish there was some way to edit a title because it seems I do that quite often.

[rondog]

I done lernt sumthin' today too! I've always wondered what that bulge was.

[oneokie]

Now I know but I don't know what a "Battkle" tank is!, fumble fingers! :roll:

I didn't even notice that little boo-boo until I came back just now, sure wish there was some way to edit a title because it seems I do that quite often.

All you have to do is ask.

[oldred]

Thank you!!!

[Calamity Jake]

Ok so now I know what that thing is, BUT what is the undercut area for on an M16/AR15 mil spec barrel?

[MaryB]

Lightening cut to save weight? On the AR...

[DeanWinchester]

Ok so now I know what that thing is, BUT what is the undercut area for on an M16/AR15 mil spec barrel?


Aint that hat got something to do with the M203 grenade launcher?

[Beagle333]

I didn't know what that bulge was either. Thanks for asking!

[MtGun44]

Grenade launcher clamp goes there. Old bbl was that size, GL made for that
diam, then they increased bbl diam, so had to leave that piece to keep the
new bbl compatible with the existing stocks of GLs.

Bill

[JeffinNZ]

I quite like to sniff a 12 gauge hull on ejection but I guess repeated 120mm gases would be over powering.

How does it work?

[popper]

I quite like to sniff a 12 gauge hull on ejection Don't you know you will get lockjaw from doing that? Some use compressed air, these are like a barrel brake with the holes pointing forward. Don't remember if the Shermans had them but the panzer & t-55? did. Naval guns use compressed air.

[MBTcustom]

Am I surprised that so many of you knew what that bulge is?
Not really.
Am I impressed?
You betcha!

[fouronesix]

The only one I got to inspect up close, including how it was put together, was on an experimental tank barrel (IIRC for an Abrams) and was mounted on a testing platform... it was being used to test projectiles and targeting systems. It was one of the "passive" types that use powder gas produced during firing. As has been posted, there are also the "active" types that use an auxiliary source of compressed air for purging the bore after firing, but have never looked at one.

Here's a link to a thread on another forum that includes a discussion on these- also has some diagrams. http://www.tank-net.com/forums/index.php?showtopic=28085

[Finster101]

Am I surprised that so many of you knew what that bulge is?
Not really.
Am I impressed?
You betcha!



I suspect there is more than one tanker on this forum. Probably ranging from Sherman to Abrams

[fastfire]

OK, it keeps the gases from entering the turret. How does it work?

[Dale in Louisiana]

It's a whopping big pain in the toot to clean! The surfaces inside the bore evacuator chamber and the surface of the barrel where it rests get coated with powder byproducts.

dale in Louisiana
(old tanker)

[375supermag]

Don't you know you will get lockjaw from doing that? Some use compressed air, these are like a barrel brake with the holes pointing forward. Don't remember if the Shermans had them but the panzer & t-55? did. Naval guns use compressed air.
Hi...

No bore evacuators on US or British Shermans during WWII...not sure without further research if any post-war Shermans may have had bore evacuators. They were re-barreled and re-armed by a large number of countries, including Israel.

No bore evacuators on German panzers.

[hardy]

Hi,I knew an old timer who was selling a rifle with a bulged barrel,he told prospective customers it was a "pressure relief valve"Don,t know if anyone fell for it.....Cheers,Mike

[fouronesix]

It's a whopping big pain in the toot to clean! The surfaces inside the bore evacuator chamber and the surface of the barrel where it rests get coated with powder byproducts.

dale in Louisiana
(old tanker)

I wasn't a tanker but when talking to the DOD technicians and Army rep about how it worked, I didn't ask that specific question, but it did come to mind later. I thought, surely, residue would build up around the ports and valves- ughh.

[Skipper]

How does it work?

https://en.wikipedia.org/wiki/Bore_evacuator
http://www.tank-net.com/forums/index.php?showtopic=28085

[Dan Cash]

A passive bore evacuator functions as follows: The bore has a series of holes ( 5 to 7 usually) drilled through the tube wall into the bore. These ports pass from the outer to the inner surface of the tube at an angle toward the muzzle. The gun tube has canister called the bore evacuator fitted with a gas tight seal over the ports. When the gun is fired and the projectile passes the ports, some of the propellant gasses are bled off into the gas tight canister and held there until the projectile exits the muzzle. Once the projectile exits the muzzle, gas pressure in the tube drops rapidly and the stored pressure in the evacuator begins to bleed back into the bore through the ports which are angled toward the muzzle.

As the gun returns to battery, shortly after the projectile clears the gun muzzle, the breech begins to open and the breech seal is broken. The high pressure gas in the bore evacuator blasts toward the muzzle and sucks the toxic fumes from breech to muzzle, preventing asphyxiation of the crew.

An active bore evacuator utilizes high pressure compressed air injected into the chamber of the gun after firing to effect bore evacuation.

[fastfire]

OK, lernt my lesson for the day, always wondered what the bulge was now I know.

[DaveInFloweryBranchGA]

Clank, Clank, I smell Tankers posting in this thread! :kidding:

[popper]

Supermag - you are correct. I was wondering when they started using them, or at least the passive ones. I sure would have hated to be a gunner in one of those, rapid fire from the main & an enclosed MG. Wow. Germans didn't much care about their people, I know the early auto guys were using rocket fuel and would often pass out from fuel fumes.

[Pb2au]

108032

[a.squibload]

"PULL"
Funny but yeah, there is a shotshell for that tank.
It's a smoothbore after all.

[Lance Boyle]

I thought we had beehive rounds for all he later tanks.

I wonder if the M60 was the first with an oem be. I'm sure the our earlier tanks were retrofitted by the folks that got the loan of them.

[Dale in Louisiana]

"Beehive" was the fire command name for the 105mm round on our M60-series tanks. The M48's had 90mm 'canister'. It came in two varieties that I knew of, one consisting of a can of pencil-eraser-sized steel pellets, the other loaded with a few thousand flechettes. Flechette? Think of an eight-penny finishing nail, except where the nail has a head, the flechette had four little tailfins.

Canister was pretty simple. When you fired it, the can stripped off at the muzzle, giving you basically a 90mm shotgun. Beehive could be muzzle-acting. The nose of the projectile had an adjustable fuse. Set for muzzle-acting, it left the muzzle, went a few yards, then popped the dispersal charge to rupture the case and distribute several thousand flechettes. That was sufficient to alter the thought patterns out to two or three hundred yards. At longer ranges, you set the range on the fuse and it would pop about 150 meters before it reached the target, giving optimum dispersal of the flechettes.

We had a lot of fun demonstrating these at the Armor Training Center. We'd put man-sized silhouette targets at 500 meters, tie balloons to them, the pop a round of beehive and watch the balloons pop.

dale in Louisiana
(Armor instructor, Armor Training Center, 1972-1974 Tanker 1969-1977)

[beagle]

Wait until you start wondering about equilibrators....... The bore evacuator is a simple device./beagle

[jaystuw]

I imagine propellant smoke must of been manageable in the turrets of tanks with low velocity small bore cannon .

In a first generation main battle tank sporting a long, big bore gun, the smoke must of been thick.

However, if I was loader in a formidable tiger tank with thick armor, a really hard hitting gun and a tough, experienced SS crew, I would suck in as much smoke as had to and still be happy that I wasn't in a lesser tank! Jay

[bob208]

m109 155mm howitzers also used them.

[Skipper]

What's 1150 10mm tungsten balls do for you? :shock:

http://www.thefirearmblog.com/blog/wp-content/uploads/2008/02/pics-soldiertech-m1028-1.jpg
https://www.youtube.com/watch?v=Cgn1nhUEgo8

[fastfire]

That's quite the camera that can follow the projectile.

[Finster101]

Yep, there was a beehive round that you could set the fuse for what range it would open up. I was in M60A1's and later got A3's. All we carried were HEAT and SABOT. As armored cav we were most likely going up against other armor and not infantry, especially on the East German/Cheque border.

[a.squibload]

[QUOTE=Skipper;2824746]What's 1150 10mm tungsten balls do for you? :shock:

DANG.
I heard it was for helicopters, what if only 3 or 4 hundred 40cal tungsten balls
hit your chopper, might be a deterrent!

[Dale in Louisiana]

Yep, there was a beehive round that you could set the fuse for what range it would open up. I was in M60A1's and later got A3's. All we carried were HEAT and SABOT. As armored cav we were most likely going up against other armor and not infantry, especially on the East German/Cheque border.

We had HEP (High Explosive Plastic), too, and a 105mm WP round, plus the Beehive. My unit in Germany was back around Frankfurt.

In Korea we were on M48A2C's and we carried, HEAT, Shot, HE and WP, all in 90mm, natch.

dale in Louisiana

[Artful]

I imagine propellant smoke must of been manageable in the turrets of tanks with low velocity small bore cannon .

In a first generation main battle tank sporting a long, big bore gun, the smoke must of been thick.

However, if I was loader in a formidable tiger tank with thick armor, a really hard hitting gun and a tough, experienced SS crew, I would suck in as much smoke as had to and still be happy that I wasn't in a lesser tank! Jay

Training film for the Sherman M4

https://www.youtube.com/watch?v=iMTjcU-kmNM