Full Version: Question with the Armor Spell
| QUOTE (algcs) |
So when I shoot at an armor plated door at the bank APDS will 1/2 the armor, but if I shoot at a similar door on an armored car the ammo acts as normal ammo?  |
Unless the bank vault has a fuel cell and the theoretical potential to move under its own power.
| QUOTE (Herald of Verjigorm) |
| Unless the bank vault has a fuel cell and the theoretical potential to move under its own power. |
Now that is a very good point. So let me see if I understand this correctly. Because the vehicle is moving it has a better chance of taking less damage because of deflection and the targets speed makes it harder to get a clean shot. If so what if the target is not moving... does armor get halved just like the door?
That is reflected, I think, in the Control Pool. Not as vehicle armour.
If shooting at a vehicular door, I would treat it as a Barrier instead of applying vehicle armour. If you are shooting for something in the vehicle instead for example, I'd apply the vehicular armour, but you may bypass it with a called shot as per the FAQ.
If shooting at a vehicular door, I would treat it as a Barrier instead of applying vehicle armour. If you are shooting for something in the vehicle instead for example, I'd apply the vehicular armour, but you may bypass it with a called shot as per the FAQ.
Hyzmarca, I'm almost certain conservation of energy is inapplicable. Amounts are being lost to heat, sound propagated through the pistol itself, etc.; momentum, on the other hand, should be conserved and ends up with a greater overall energy for a lighter projectile. I am, however, tired and may be wrong, but I'm pretty sure you can't define that as an energy-closed system.
~J
~J
It doesn't really matter whether the system is energy-closed or not, really. The reason APDS ammo punches through barriers better than regular ammo is because regular ammo is made of lead or similar materials that deform and expand on impact with a barrier, while APDS ammo is built to have a smaller area of impact. It's the same reason an ice pick punches through barriers better than a hammer: it's the same amount of kinetic energy being transferred, but the ice pick focuses it all on a much smaller area, making it easier to punch a hole in something. Regular ammo actually does more damage to a target because it transfers more of its kinetic energy to the target, but when it strikes a barrier more of the kinetic energy is also transferred to the barrier for that same reason. APDS slips right through the barrier because it doesn't deform, leaves a smaller footprint on the barrier, and passes through, retaining more of its energy.
Right, I'm not debating the transferral of energy to the target, just the energy of the projectile. More importantly for me here, this is an area that I usually like to consider myself moderately proficient in, so if I'm making a gross error I'd like to confirm that so that I can avoid it in the future.
~J
~J
If you step back far enough the universe can't be deflined as a closed energy system. But, I'm not going to turn this into a discussion of vacume energy. In physics, we arbitrarilary define closed systems and make assumptions because there would be an impossible number of variables otherwise. For the most part, these ignored variables are negligable and resulting errors filtered out by using significant figures.
Anyway, conservation of momentum only applies when two objects impact or one moving object splits into two or more.
In that case Mi(Vi) + Mii(Vii) = Miii(Viii) This also relates to Newton's third law and may effect the energy of APDS when the sabot is discarded.
I've just recently finished a long hard physics final so I've been thinking about these problems most of the day.
Yes, there will be energy lost through friction. Some energy converted to rotational energy because of the rifling. However, we can ignore both of these for the point of this problem since they would be uniform depending on the barrel. Rotational acceleration of the bullet is porportional to linear acceleration depending on the rifling of the barrel and rotational energy is calculated the same way as tangential energy, so rotational energies will be the same in both bullets as well.
If a powder charge and barrel length are such that it imparts a bullet with 215J or energy it will do so no matter how massive the bullet is. Provided the bullets have the same area, of course.
Traditional sabot creates a better seal in the barrel and increases the pressure on the bullet, but APDS is essentialy a regular bullet while in the barrel. In this case, the sabot allows a smaller bullet to be used, but it is probably made out of unusualy dense materials such as tungstun or depleted uranium as armor-piercing bullets often are.
There are numberious variables that would change the bullet's energy including barrel length, rifling, powder charge, and caliber but mass is not one of them.
Providing that everything else is the same, mass makes no difference in relation to the the force of the bullets impact or the bullet's kenetic energy.
However, the more massive bullet has greater momentum.
20*.005 = .10
14*.01 = .14
In this case, twice the mass means two-fifths more momentum. This is the advantage of heavier bullets.
Anyway, conservation of momentum only applies when two objects impact or one moving object splits into two or more.
In that case Mi(Vi) + Mii(Vii) = Miii(Viii) This also relates to Newton's third law and may effect the energy of APDS when the sabot is discarded.
I've just recently finished a long hard physics final so I've been thinking about these problems most of the day.
Yes, there will be energy lost through friction. Some energy converted to rotational energy because of the rifling. However, we can ignore both of these for the point of this problem since they would be uniform depending on the barrel. Rotational acceleration of the bullet is porportional to linear acceleration depending on the rifling of the barrel and rotational energy is calculated the same way as tangential energy, so rotational energies will be the same in both bullets as well.
If a powder charge and barrel length are such that it imparts a bullet with 215J or energy it will do so no matter how massive the bullet is. Provided the bullets have the same area, of course.
Traditional sabot creates a better seal in the barrel and increases the pressure on the bullet, but APDS is essentialy a regular bullet while in the barrel. In this case, the sabot allows a smaller bullet to be used, but it is probably made out of unusualy dense materials such as tungstun or depleted uranium as armor-piercing bullets often are.
There are numberious variables that would change the bullet's energy including barrel length, rifling, powder charge, and caliber but mass is not one of them.
Providing that everything else is the same, mass makes no difference in relation to the the force of the bullets impact or the bullet's kenetic energy.
However, the more massive bullet has greater momentum.
20*.005 = .10
14*.01 = .14
In this case, twice the mass means two-fifths more momentum. This is the advantage of heavier bullets.
Somebody put it in non-geek terms!
As far as I'm concerned, the spell creates (or increases existing (?)) armor. APDS is designed to penetrate armor. APDS halves the armor from the Armor spell.
If you want an APDS Barrier spell, then design one.
As far as I'm concerned, the spell creates (or increases existing (?)) armor. APDS is designed to penetrate armor. APDS halves the armor from the Armor spell.
If you want an APDS Barrier spell, then design one.
Non Geek terms: An armour piercing bullet doesn't have more energy than any other when it strikes the target, because the same amount of energy is put in to it from the gun. It does, however, have more momentum. It also doesn't deform, so it loses less of its energy when it hits a barrier of some kind.
So with an armour spell, imagine it as a thin force field. Within that field, a force is applied to anything, pushing away from the person being protected. An APDS round would, due to it's small size and the Discarding Sabot bit (or something, I don't really know much about Discarding Sabots, only the physics part), have less total force effecting it as it passed through the barrier, and thus would be slowed down less than a normal bullet.
JaronK
So with an armour spell, imagine it as a thin force field. Within that field, a force is applied to anything, pushing away from the person being protected. An APDS round would, due to it's small size and the Discarding Sabot bit (or something, I don't really know much about Discarding Sabots, only the physics part), have less total force effecting it as it passed through the barrier, and thus would be slowed down less than a normal bullet.
JaronK
Cool, so what I said. Thanks. 
Also, since sabot rounds have a smaller cross-dimensional area, they encounter less wind resistance slowing down the bullet while traveling down range. This probably has a negligible impact on SR combat, since it mostly occurs at very close range, but has big effect at 2km tank engagement ranges.
hyzmarca has a good point, but it doesn't quite hold. The same amount of the same propellant in the same cartridge fired out of the same weapon can produce different amounts of kinetic energy at the muzzle depending on what bullet is used. Also, some armor piercing ammunition designs do in fact use more propellant.
.50 BMG M2 Ball (FMJ) fired out of an M2HB HMG:
235gr propellant (type WC 860), 662gr projectile, velocity (78ft from muzzle) 2810fps
11610 ft-lbs
.50 BMG Mk 211 Mod 0 API:
233gr propellant (WC 860/MR 5010 or RA-NC-167), 671gr projectile, velocity 2910fps
12620 ft-lbs
This round is full-caliber with a subcaliber penetrator that will separate on impact.
.50 BMG M903 SLAP ("APDS"):
275gr propellant (WC 856, faster burn speed I would imagine), 360gr projectile, velocity 4000 fps
12793 ft-lbs
Saboted armor piercing penetrator, 0.3" (7.62mm)
What Apathy said about wind resistance certainly applies to the M903 compared to the M2 Ball.
.50 BMG M2 Ball (FMJ) fired out of an M2HB HMG:
235gr propellant (type WC 860), 662gr projectile, velocity (78ft from muzzle) 2810fps
11610 ft-lbs
.50 BMG Mk 211 Mod 0 API:
233gr propellant (WC 860/MR 5010 or RA-NC-167), 671gr projectile, velocity 2910fps
12620 ft-lbs
This round is full-caliber with a subcaliber penetrator that will separate on impact.
.50 BMG M903 SLAP ("APDS"):
275gr propellant (WC 856, faster burn speed I would imagine), 360gr projectile, velocity 4000 fps
12793 ft-lbs
Saboted armor piercing penetrator, 0.3" (7.62mm)
What Apathy said about wind resistance certainly applies to the M903 compared to the M2 Ball.
| QUOTE (Eyeless Blonde) |
| It's the same reason an ice pick punches through barriers better than a hammer: it's the same amount of kinetic energy being transferred, but the ice pick focuses it all on a much smaller area, making it easier to punch a hole in something. Regular ammo actually does more damage to a target because it transfers more of its kinetic energy to the target, but when it strikes a barrier more of the kinetic energy is also transferred to the barrier for that same reason. APDS slips right through the barrier because it doesn't deform, leaves a smaller footprint on the barrier, and passes through, retaining more of its energy. |
This is mostly true, although I do shudder whenever someone says damage caused has to do with "transfer of kinetic energy". Also, many (most) FMJ ammunition does not deform when it hits living tissue, but it does deform when it hits armor. In these cases, using a full-caliber armor piercing round instead will allow you to keep the size of wound cavity while increasing armor penetrating ability immensely.
| QUOTE (JaronK) |
| Non Geek terms: An armour piercing bullet doesn't have more energy than any other when it strikes the target, because the same amount of energy is put in to it from the gun. It does, however, have more momentum. |
It was hard to isolate this from hyzmarca's post, so I'm quoting this instead. This is more addressed to hyzmarca.
This depends completely on the specific ammunition design. Amor piercing designs can be heavier and slower, lighter and faster, heavier and faster, or even lighter and slower (if poorly designed).
The 5.56x45mm M995 tungsten-core full-caliber armor piercing round is lighter (52gr vs 62gr) than the respective standard FMJ round (M855), and is much faster (3324fps vs 3025fps), and the same more or less goes for the 7.62x51mm M993 AP vs M80 FMJ (126.6gr vs 146gr, 2985 fps vs 2750 fps). In both these cases, the AP designs have more muzzle energy, though only barely: 1276 ft-lbs vs. 1260 ft-lbs, 2505 ft-lbs vs. 2452 ft-lbs. The propellant amount is the same for 7.62x51mm, slightly more propellant in the M995 5.56x45mm.
The reason for the lower weight in most cases is that the penetrating core (although of a much denser material than basic FMJ design cores) is slightly smaller in diameter and often doesn't fill the whole jacket (the penetrating core doesn't have such a small-angle, sharp point).
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