[High-Tech] Understanding the practical rate of fire for a cannon.

[The_Ryujin]

Originally Posted by Michael Thayne

• If you have a cannon with something like Shots 1(4) crewed by a gunner and a loader, can the gunner take Aim maneuvers while the loader is taking a series of Ready maneuvers to load the weapon? Or does the gunner have to wait until the loader is done loading before the gunner can start taking aiming?

Assuming you're talking about a situation where the cannon is attached to a turret like with a tank then yes. The gunner or commander can aim while the loader loads. If set up like an say an artillery piece then in most cases no, aiming and loading has to be done separately.

Originally Posted by Michael Thayne

• What does the fractional RoF for the Motovilikha D-81TM (the big Russian tank gun) in High-Tech mean? Does it mean it takes eight maneuvers for the gunner to fire? Or just that the gunner has to wait 7 seconds between attacks for the autoloader to reload the gun? In the latter case, can the gunner take Aim maneuvers while the autoloader is doing its thing?

The ROF of 1/8 is a typo. It should say ROF 1 Shots 1(8).

[The Colonel]

IIRC the rule always used to be that whilst the gunner was engaging his target, the commander was already locating and fixing the bearing for the next one, and the loader would be feeding the gun as the gunner traversed between targets... and I'm told that modern gunnery control systems can stack targets several high and track them simultaneously...

[Fred Brackin]

Originally Posted by Michael Thayne

I A 60 metric ton tank firing a 7 kilogram shell has about the same ratio of platform mass : projectile mass as a 75 kilogram hunter firing a 9 gram bullet. And I think similar logic would apply to how much chambering the round is going to throw off your aim. I admit there might be a disanalogy I'm missing.
)

Recoil comes not only from projectile mass but from the mass of propellant and the velocity of both. So if the Rapira tank cannon in HT throws a proportionate projectile at 2x the velocity of a common hunting bullet that's a minimum of 2x the recoil.

There's more propellant too. The round for the Rapira in HT weighs 73 lbs (a litle over 33 kilos) and no more than an end cap of that is brass. There's some that"s sabot but mostly it's projectile and propellant. You get recoil fro, the sabot anyway.

So if that 9 gram bullet is approximately what I think it is it's more like 11 grams once you add the propellant. That's a ratio of mass of hunter to fired round of around 6800 to 1. The ratio of the tank to the fired tank round is more like 1800 to 1.

So you're geting proportionately much more recoil.

That hunter can't Aim his rifle while he's firing it anyway. I wouldn't let him Aim while he's working the bolt either. Working the bolt moves the gun.

[Michael Thayne]

Originally Posted by The_Ryujin

Assuming you're talking about a situation where the cannon is attached to a turret like with a tank then yes. The gunner or commander can aim while the loader loads. If set up like an say an artillery piece then in most cases no, aiming and loading has to be done separately.

The ROF of 1/8 is a typo. It should say ROF 1 Shots 1(8).

The errata actually gives it "Shots 22(60i)", with a note about the autoloader taking 7 seconds to do its thing.

[thrash]

Originally Posted by The Colonel

IIRC the rule always used to be that whilst the gunner was engaging his target, the commander was already locating and fixing the bearing for the next one, and the loader would be feeding the gun as the gunner traversed between targets...

That's the way I remember (M60A3) tank gunnery: the time between engagements was determined by how long the loader took, because by then the gunner was already on target.

(My squadron commander thought it would be cool for aviation lieutenants to experience tank gunnery for themselves, so I did one firing table as a loader. Broke my toe when I let my foot get in the way of a spent casing, but impressed the crew because I continued to load without missing a beat.)

Don't forget, modern tank and artillery guns have shock absorbers for the recoil that return the barrel to its original position. The vehicle bounces around some, but the target is probably moving (or changed, after a successful hit), too.

[Eukie]

For post-war tanks it depends on the design of the sight and loading mechanism. Some systems allow the gunner to maintain a sight picture while gun is being reloaded, other systems don't. The former is somewhat rare, and fine adjustments to aim cannot typically be made while the loader is reloading the gun, but a precise answer would have to be on a per-tank basis.

[Rupert]

Originally Posted by Ulzgoroth

Addendum: Automatic loading assists often require the gun go to a particular elevation to work. That would probably interfere with aiming, unless the gunner's sight somehow disengages from the gun and then re-aligns. Which seems like it probably wouldn't be accurate.

Actually, that's very often how they work. Rather than trying to fully stabilise the whole weight of the gun, only the sights are fully stabilised and they are not mechanically linked to the gun. When you want to fire either the gun is synced to the sights or the system fires the gun at is senses it passing through the correct line.

Aside from anything else, for manually loaded guns if they were stabilised when being loaded the loader would get smashed by them if the tank went over a bump. So they get stabilised in that they don't bounce all over, but they aren't locked onto a target all the time.

At the most massive end, big naval guns in the 20th century had next to no connection to their sights, which were often in a completely different part of the ship (though the turrets often had backup sights), and the sight and rangefinder operators most certainly kept doing their thing while the guns were being reloaded, as did the fire control computer operators, etc. That said, with these guns while the turrets would be constantly trained, the guns' elevation was adjusted after loading, even if they were loaded without being moved to a fixed elevation - they were just too heavy for it to be safe having them moving while their crews were serving them.

[Rupert]

Originally Posted by Ulzgoroth

How do you imagine the gun being mounted that it would be able to move relative to the turret under those forces without breaking the training mechanism and effectively disarming the tank?

Lots of tanks other than the T-72 family use autoloaders. Aside from Russian tanks, they can be found in US light vehicles (Stryker MGS), as well as in Chinese, Japanese, French, and Korean main battle tanks.

It's not impossible to have an autoloader that draws from an isolated ammo compartment rather than putting the magazine in the fighting compartment, and reportedly some modern ones do. Cold-war era soviet models did have that issue, though.

Also the T-64 family have an autoloader, and it's not the same as the T-72 family's. The thing about the carousel/cassette design the Soviets/Russian use is that it's reasonably fast, even with the separate shell and charge that they use. Systems that load from flash-tight boxes tend to be slower, larger, and/or more complex, neither of which is great in a tank in a war. They're probably okay in self-propelled artillery (where they have more space), though and that's one use for them today.

[Ulzgoroth]

Originally Posted by Rupert

Actually, that's very often how they work. Rather than trying to fully stabilise the whole weight of the gun, only the sights are fully stabilised and they are not mechanically linked to the gun. When you want to fire either the gun is synced to the sights or the system fires the gun at is senses it passing through the correct line.

Huh. That certainly solves problems, but I am surprised it's precise enough to be considered satisfactory.

Originally Posted by Rupert

At the most massive end, big naval guns in the 20th century had next to no connection to their sights, which were often in a completely different part of the ship (though the turrets often had backup sights), and the sight and rangefinder operators most certainly kept doing their thing while the guns were being reloaded, as did the fire control computer operators, etc. That said, with these guns while the turrets would be constantly trained, the guns' elevation was adjusted after loading, even if they were loaded without being moved to a fixed elevation - they were just too heavy for it to be safe having them moving while their crews were serving them.

Sure, but big naval guns accept quite a lot of scatter.