5cm and 7.5cm Bordkanone

[davebender]

How reliable were auto loaders in these weapons?

If reliable I think Hetzer 7.5cm SP AT gun would have benefitted greatly from an auto loader as vehicle was so cramped.

 

[Erich]

too slow to fire and be effective, recoil was heavy on any of the LW A/C

 

[tomo pauk]

What was the RoF, Eric?

 

[davebender]

BK 5cm cannon
BK 5 cannon - Wikipedia, the free encyclopedia
45 rounds per minute.
22 round magazine.

BK 7.5cm cannon
7.5 cm BK (Bordkanone 7.5 cm)
30 rounds per minute
10 round magazine.

BK cannon reload time might be too slow for aircraft use but it's plenty fast for an AFV auto loader. However the auto loader must be reliable. Were they?

 

[Shortround6]

A reliable auto loader using WW II technology would be bigger than the human loader.

Auto loader has to fixed ( not moving in relation to gun breech) to the gun.

 

[Erich]

note how many rounds carried, now granted the Me 410 with the Bk 5cm did do damage against US heavies but wondering just how many shots by the crews missed their targets. the Hs 129 with the 7.5cm....oh my gosh how vulnerable and low altitude which used as a flat out tactic against Soviet armor, heavy beast.

 

[tomo pauk]

A reliable auto loader using WW II technology would be bigger than the human loader.

Auto loader has to fixed ( not moving in relation to gun breech) to the gun.

You mean the auto-loader will remain static vs. the gun's cradle, since breech moves after firing?
All of that set-up needs to be turned upside-down if it's to work in the confines of the AFV, thanks for the pic. One wonders whether the ammo 'circle' could be 'wrapped around' the cannon, so the AFV installation is more compact.

 

[davebender]

That how the BK 5 cannon worked. Looks pretty compact to me.

 

[Shortround6]

You may have phrased it better Tomo. the State of the art in WW II did not allow for the magazine to be fixed (stationary) in the vehicle and the gun to elevate and traverse changing angles and distances to the magazine. It took quite a number of years to get around this and the first post war vehicles to use auto-loaders used "fixed" magazines.

See AMX-13:

The turret bustle held two 6 round magazines. Another 24-25 rounds were in the hull of the tank but required the crew to dismount and load the magazines from outside the tank. Two magazines also meant that two types of ammo were available without having to unload the magazine, although that does mean less of each available. Not a problem in an anti-tank aircraft, load it up with AP and go for it. More of a problem for an AFV. You need HE rounds but the round up the spout is AP and so are the next 8 in the magazine?? or vice versa? Please note that the whole upper turret elevated together, it was trunioned about mid turret.

Swedish S tank was next with an auto loader.

Gun was fixed in the hull and the driver acted as the gunner, pivoting the tank for traverse and using the hydro-pneumatic suspension system for elevation.

The problem in a vehicle like the Hetzer, which had a rather restricted traverse to begin with is not only is the gun breech/cradle waving about inside the vehicle, but now you want a huge magazine moving about inside also.

How far can you traverse or elevate/depress before the magazine housing hits the walls/roof of the hull let alone the crew that are left inside.

 

[davebender]

Hetzer was too much gun and armor on too little chassis. It's never going to be perfect. However an autoloader might have helped. It also puts one less crew member in harms way.

 

[Denniss]

BK 5cm cannon, 45 rounds per minute.

BK 7.5cm cannon, 30 rounds per minute

How on earth should this be possible? Not even the tank variants were able to fire that many rounds per minute (not even close).

 

[davebender]

3.7cm Flak 43 could fire 250 rounds per minute. MG42 machinegun could fire 1,200 rounds per minute How is that possible?

Auto loading is faster then having a human manually load rounds into the weapon chamber.

 

[Denniss]

No, not even with a belt feed of some sort is it possible to achive such a high rof - way too much mass on the move. The MG 42 was actually able to keep this rof (and even higher) but was limited by ammo belt length and overheating barrel.

 

[Shortround6]

How on earth should this be possible? Not even the tank variants were able to fire that many rounds per minute (not even close).

Tank guns usually fired slower than the same gun in an towed AT gun mount. Towed mount had more room to work and usually had more loaders ( man loaded the gun while a second (or even third) got the ammo from the containers and slapped it into the loaders hands. Tank loader had to get the ammo himself from the racks/bins.


(davebender)
A worthwhile auto loader wasn't going to fit in a Hetzer without too many other sacrifices (like even less traverse).

A problem that many 3 man AFVs faced (little thought of until they were in service) is there is one less man to pull routine maintenance, cook and guard duty. And now you have to maintain the auto loader. You can shift some of the maintenance to higher echelon but that requires a bit of planning and manpower shuffling.

 

[Jack_Hill]

Autoloading guns is an appealing idea for sure..
German engeeniers certainly had it in mind.
Guess was not done because : weight and gun balance could only be countered by heavy electrical/hydraulic means, for just a slighter higher RoF and traverse loss..
As said before, losing the versatility of one crew member.

 

[tomo pauk]

No, not even with a belt feed of some sort is it possible to achive such a high rof - way too much mass on the move. The MG 42 was actually able to keep this rof (and even higher) but was limited by ammo belt length and overheating barrel.

The 30 rpm would be the cyclic (theoretical) rate of fire, or a shell is fired every two seconds. The 75mm Skysweeper was managing 45 rpm, again cyclic.
And then Oto Melara come in

Soviet 57mm AAA (various post-war guns) was able to spit out 120 rpm, cyclic.

 

[davebender]

I wouldn't want an auto loader in a MBT.

15 ton SP AT gun such as the Hetzer is a different matter. Such a small AFV cannot remain in the front line for long as it's vulnerable to artillery fire that a larger armored vehicle would shrug off. After emptying the 10 round auto loader magazine it's time to scoot.

 

[Jack_Hill]

Absolutly right Dave.
It may be a simple personal thought of my own that fighting in such a small death coffin, I personaly would prefer a good, confident,reliable comrade than an autoloader.
An autoloader cannot help for crew extraction in case of fire or battle damage.
A crew fellow can.
Just my opinion, worth what it worth.

 

[davebender]

If Germany had GDP similiar to USA they would produce 1,000 Panther tanks per month and inexpensive 15 ton death coffins wouldn't be necessary.

 

[Jack_Hill]

Ok once more.