69 replies to this topic

[Viper69]

We have come full circle.

[Death Mallet]

Xandre Blackheart, on 26 June 2012 - 12:12 PM, said:

Pointless? Nah. Physics dont' change. Advances in material sciences might make it more viable to have faster mechanisms, but the primary issue is still armor penetration. It's difficult to forsee technologies that would make one large shell inferior to multiple small shells at armor penetration. I probably rambled a bit but that was the point of the whole post. Any efficiences in a properly designed "auto cannon" intended for armor pericing would be directed towards firing larger shells faster (more efficiently), not even more smaller shells faster (more efficiently).

Except for the part where this is demonstrably false.

Pretty much the best anti-armor gun ever invented is the GAU-8 Avenger mounted on the A-10 which was explicitly designed for close air support tank killing.

http://en.wikipedia....i/GAU-8_Avenger

Shoots up to 4200rpm



That would be your rotary autocannon. A regular autocannon would fire at about 1/10 that rate. . . or about as fast as a normal machine gun.


The expertise of real world weapons designers and 30+ years of outstanding combat history says high rate of fire makes for an excellent anti-armor weapon.


. . . and anyway most of the fluff says autocannons are what they actually are. Fully automatic.

Edited by Death Mallet, 28 June 2012 - 09:35 AM.

[Viper69]

So the single discarding sabot tungsten penetrator of an M1 Abrams is less effective than slinging a 1,000 rounds downrange on a target? I think there are a few T72s that would think otherwise. Both are quite effective and achieve the same results through different means. The GAU attacks the soft upper armor of a tank with a boat loads of round where as the sabot attacks the sides,front anything but top.

Edited by Viper69, 28 June 2012 - 09:38 AM.

[Xandre Blackheart]

I think the above poster already beat me to it. Do you think they'd be using a 30 MM if weight wasn't a primary restriction on a flying platform? If they could afford the weight ask yourself if they wouldn't have gone with say a 40mm? Well if it's only a bit slower, still within the realm of possibility. But the other limitation on a gunship is fire control. At some point the rate of fire will slow to the point where you can't strafe, and that means the gun becomes useless to a fast attack craft.

That's why most anti-armor air carry HELLFIRE as their PRIMARY anti-armor weapon. But that's a missile and outside the scope of the discussion, other than pointing out that the 30mm is the secondary weapon. (and I've seen it fired on range in real life and yes it is awesome.)

I also have real world experience you see. I've driven (and commanded) armored vehicles, fired them, worked in large armor formations, cursed then when the tracks break and I have to get in the mud and sand, run scout vehicles (never ever volunteer to ride in the back of a Bradley M2 unless they used locktite on the bolts holding the interior armor on), and jockeyed on a few helicopters (but sadly no gunships- I only got to see those tested from the ground)

The advantage of a gunship or a-10 is the angle of attack. From above where armor is an afterthought. It can afford to carry a lighter weapon, and this is good engineering. It exploits a weakness in current armor design and makes it efficient.

If it was feasible to armor the tops of armored vehicles as well as they do the sides (again weight is a factor) the 30mm would lose it's effectiveness against MBT's very quickly. At that point the 30mm would be replaced by additional missile hard-points, or be relegated to soft skin targets.

There's a reason they don't mount those gatlings things as the main gun on an Abrams you know.

[JokerPW]

Comparing to MW4 (and Mercenaries 4)
Autocannon: short sequence of fire.
Gauss Rifle: single bullet
LBX: kind like a gigant shotgun
Machine gun: "crap" (lol)
Rotary cannon: Bigger machine gun that actually does damage.

The bigger the damage, the bigger the projectile. That would explain (technically, in an imaginary future) why the range decreases !

Hope it answer ! =]

[Steel Talon]

AC/20,10 should not loose damage with range, cause they are using HEAT type shells, which dont relly on kinetic energy
HEAT = High Explosive Anti Tank

[Xandre Blackheart]

Yeah the shorter range is difficult to reconcile.

The only way you can make any sense of it is if they are using a standard load charge for each projectile regardless of caliber.

And I just can't think of a logical reason why that would be.

[Viper69]

Our biggest problem is we are trying to wrap our heads around a future weapon with modern examples.

[Xandre Blackheart]

Well that's half the fun.

[Viper69]

Very true!. To be fair though, the gun on an Abrams is 120mm smooth bore but its actual penetrator is only about 30-40mm in diameter. However its the velocity and the kinetic discharge when it hits that does the bulk of the damage. I think we could interpret the shell casing we see in the old art as multiple rounds of combat taking place. Not a stream of rounds that coalesce into the 20 points of damage.

Edited by Viper69, 28 June 2012 - 12:41 PM.

[Death Mallet]

Care to do a kill count comparison between A10s and Abrams over their service life?

Thought not.

Your point about shooting down on the tops of tanks is valid, and well taken. . . but why "in real life" would it be any different for a 100 ton mech that is shooting down on the tops of the medium mechs around it. You'd want the ROF to increase the likelyhood of hits.

An assault mech using the 120mm equivalent in a battletech "real world" scenario against the lightly armored tops of medium mechs around it would be like taking a bazooka to a cockroach. Battlemechs being what they are they'd probably carry both for dealing with each kind of threat.

. . . all of which is irrelevant.

The point is that autocannons are rapid fire weapons both in BT fluff and real life.

Edited by Death Mallet, 28 June 2012 - 01:36 PM.

[PewPew]

Xandre Blackheart, on 28 June 2012 - 11:10 AM, said:

Yeah the shorter range is difficult to reconcile.

The only way you can make any sense of it is if they are using a standard load charge for each projectile regardless of caliber.

And I just can't think of a logical reason why that would be.

Maybe standardization of round size or something. I imagine firing an AC20 round the same distance as an AC2 round would require a lot more propellant, making the entire cartridge either too large or too much if a liability to store.

I like to imagine that the shorter range weapons in the BT universe came AFTER mech warfare became standard. Mech warfare eventually developed into close-range affairs because of mech armour being able to take a beating. Because engagements took so long, to ensure your enemy was out of the fight required riskier, close range fighting. Since many engagements were already happening at close range, weapon developers decided it was better to put a higher ratio of explosives to propellant in AC rounds.

Of course, we know that the gauss, and other, long range hard hitting weapons came afterwards chronologically. This allowed pilots to do significant damage at long range once again against mech armour.

[PewPew]

Does anyone else just see the Battletech universe as just a sci-fi reflection of the medieval period of Europe? Aside from the political likeness, the weapon tech follows a similar pattern too.

Armour got so heavy that what was once a simple matter of putting a blade to your opponent with a reasonable amount of force became so much more complicated. Swords had to get bigger, people started using more hammers and other blunt weapons, and of course, people eventually developed the crossbow.

[Agent CraZy DiP]

I think they should just add both a large caliber single shot cannon, and a small caliber burst fire cannon. Why not? They do the same dps right? Some people prefer to risk taking the single shot, some people aren't as good at aiming and would prefer a burst/rapid fire weapon.

[RedDragon]

PewPew, on 28 June 2012 - 04:37 PM, said:

Maybe standardization of round size or something. I imagine firing an AC20 round the same distance as an AC2 round would require a lot more propellant, making the entire cartridge either too large or too much if a liability to store.

I like to imagine that the shorter range weapons in the BT universe came AFTER mech warfare became standard. Mech warfare eventually developed into close-range affairs because of mech armour being able to take a beating. Because engagements took so long, to ensure your enemy was out of the fight required riskier, close range fighting. Since many engagements were already happening at close range, weapon developers decided it was better to put a higher ratio of explosives to propellant in AC rounds.

Now that you mention it, according to the TechManual, the AC/2 and /5 are in fact the first ACs to be developed. The "larger" classes followed later on.

[Vilheim]

Xandre Blackheart, on 28 June 2012 - 11:10 AM, said:

Yeah the shorter range is difficult to reconcile.

The only way you can make any sense of it is if they are using a standard load charge for each projectile regardless of caliber.

And I just can't think of a logical reason why that would be.

Here's a thought. Let's say that the amount of propellant on a round is proportional to the diameter of the shell.
So, x amount of propellant for y diameter, 3x propellant for 3y diameter.
Now suppose, y diameter for V volume of shell, which has an approximately uniform density, leading to M mass.
However, diameter and volume are not directly proportional. 3y diameter != 3V volume, in fact if you do the calculus it should be considerably greater.
This leads to a dis-proportionally larger mass of the shell as the diameter of the round increases, and since the amount of propellant only increases in linear fashion, the propellant can not "keep up" with the extra mass required to fire the shell, and therefore, a higher caliber shell has less range.

I'm probably wrong, but it's worth a shot.

[Viper69]

Death Mallet, on 28 June 2012 - 01:35 PM, said:

Care to do a kill count comparison between A10s and Abrams over their service life?

Thought not.

You want to throw some numbers out, then do it. How about kills per rounds expended? Since you brought up the numbers, you bring them to the table, dont just leave it hanging there. Also we are not talking about all the cars and trucks on highways, armored vehicles using the GAU gun and not missiles. I will bet you 1 saltine cracker that the Abrams has a higher kill to round expended ratio than the A10. So you tell me which is more efficient, spraying a crapton of rounds out or one high kinetic damage shot.

I suppose you will get back to me with your stats, if not I will take that as an empty argument you tossed out.

[Xandre Blackheart]

Death Mallet, on 28 June 2012 - 01:35 PM, said:

Care to do a kill count comparison between A10s and Abrams over their service life?

Thought not.

Your point about shooting down on the tops of tanks is valid, and well taken. . . but why "in real life" would it be any different for a 100 ton mech that is shooting down on the tops of the medium mechs around it. You'd want the ROF to increase the likelyhood of hits.

An assault mech using the 120mm equivalent in a battletech "real world" scenario against the lightly armored tops of medium mechs around it would be like taking a bazooka to a cockroach. Battlemechs being what they are they'd probably carry both for dealing with each kind of threat.

. . . all of which is irrelevant.

The point is that autocannons are rapid fire weapons both in BT fluff and real life.

An auto cannon is an auto loading cannon. No one ever said anything different. The issue is that you insist that is HAS to be rapid and the more rapid the better. And that is patently false. For armor penetration it's kinetic damage (or explosive damage but larger shells win there also) which benefits tremendously from MASS.

As for kill counts that's a factor of usage. There just isn't as much call for Main battle tanks since the collapse of the Soviet union so kill count is really useless for comparison. Especially a total kill count. That's statistically useless. You would have to do something like a kill count per shell fired for it to have any meaning other than just being a spurious argument.

Care to compare the actual penetration specs on armor? The M829A1(that's the first generation Abrams sabot) penetrates roughly 620 mm of steel at 1000m. The current round is the M829A3 and the technical are classified but there are estimates of up to 800mm of penetration at 1000m.

The GAU-8 has a penetration of steel armor at 38mm at 1000m. If it wasn't mounted on a flying platform it would be damn near useless against a modern tank. Probably still rip the hell out of soft targets though. But hell a .50cal can do that.

That is a HUGE difference in penetration, and illustrates the point of kinetic energy being increased by MASS as well as velocity. Firing a butt load of smaller bullets isn't going to yield more penetration. Even the GAU-8, a supremely accurate Gatling has a 10' spread at 2000ft. You just aren't likely to hit the same spot more than once or twice before you over heat or use up your ammo load.

Your point about larger mechs firing down on top of smaller mechs is unrealistic also, well from the fluff point of view anyway. Mechs have armor all around, except for the rear and the cockpit. They aren't designed like an armored vehicle with a softer top to save weight. But the telling point is that there really isn't THAT much height difference even between a Commando and an Atlas, until you get right up next to each other. So sorry that's not an example of consistent mechanics. Good try though. There are rules for VTOL's gaining extra chances for cockpit/head shots in the rules however, so they did take that dynamic into some account.

You can make a point for rapid fire from the fluff, but real world physics will always yield better penetration from a larger mass moving at a higher velocity. P=MV. Mass times velocity.

But since we've all decided to go with a breaker burster theory for auto canons, the argument is moot when applied to the BT universe.

Just don't try to tell a tanker they should swap out their Main gun for a Gatling.

[Xandre Blackheart]

PewPew, on 28 June 2012 - 04:48 PM, said:

Armour got so heavy that what was once a simple matter of putting a blade to your opponent with a reasonable amount of force became so much more complicated. Swords had to get bigger, people started using more hammers and other blunt weapons, and of course, people eventually developed the crossbow.

That's not just the medieval arms tech race that's the entire history of warfare, ever since some tribesman found out he could block spears better with a thicker hide shield. You can look at WW2 if you want a classic example of armor getting thicker and thicker, forcing larger guns. Or look at the cold war development of MBT's also. The BT universe also follows that dialectic.

Agent CraZy DiP, on 28 June 2012 - 05:18 PM, said:

I think they should just add both a large caliber single shot cannon, and a small caliber burst fire cannon. Why not? They do the same dps right? Some people prefer to risk taking the single shot, some people aren't as good at aiming and would prefer a burst/rapid fire weapon.

Maybe they could make that the dynamic for the LBX... I never saw that much use for them anyway, since SRM's already exist...

[Xandre Blackheart]

Vilheim, on 28 June 2012 - 05:35 PM, said:

Here's a thought. Let's say that the amount of propellant on a round is proportional to the diameter of the shell.
So, x amount of propellant for y diameter, 3x propellant for 3y diameter.
Now suppose, y diameter for V volume of shell, which has an approximately uniform density, leading to M mass.
However, diameter and volume are not directly proportional. 3y diameter != 3V volume, in fact if you do the calculus it should be considerably greater.
This leads to a dis-proportionally larger mass of the shell as the diameter of the round increases, and since the amount of propellant only increases in linear fashion, the propellant can not "keep up" with the extra mass required to fire the shell, and therefore, a higher caliber shell has less range.

I'm probably wrong, but it's worth a shot.

Well no you're not wrong. It's definitely not a linear formula. If propelling a 1kg shell at 1000m/s takes X propellant. it is definitely more then X2 propellant to propel a 2kg shell at 1000m/s

The point where you go off the rails a bit is that it's mass, not volume or diameter that makes the difference. If you used the same diameter bore, and a denser shell, you'd see the same results.