Different Gyroc Designs

[Rupert]

Originally Posted by AlexanderHowl

While gyrocs sound cool, their performance in Ultratech leaves something to be desired. Weapons that use gyroc ammunition should be lighter and cheaper than conventional weapons, as they do not have to contain the stress of the detonation that accelerates conventional ammunition, and they should have a lower ST requirement and a lower recoil, since the user does not have to absorb the impulse from the detonation of conventional ammunition. In essence, they should probably have half the unloaded weight and base cost, with -2 to minimum ST and -2 to Rcl (minimum Rcl 1).

If you look at UT's gyrocs, they are very light (aside from the LSW, which is oddly heavy), do have low MinST levels, and they all have Rcl 1. The weapon stats are not the problem.

When it comes to ammunition though, pistols and SMGs should probably not be gyrocs (pistol and SMG rounds are just too short to justify the rocket engines), meaning that only longarms should be gyrocs. They should not have rifling, as spin is a negative for rockets, and should instead depend on a flat trajectory (no real change in Acc, just an explanation of the differences).

In the real world, gyrojet made pistols more than rifles, and they did spin - spinning is actually quite a common method of stabilising rockets in the real world. The reason gyrocs aren't great in pistols is the short engagements ranges of pistols.

15mm should probably be the minimum size, and 18.5mm and 25mm should also be available. Ammunition costs should probably by 8× for 15mm, 4x for 18.5mm, and 2× for 25mm to represent the expense of miniaturization. Viper rounds are +300% the base gyroc cost.

RL gyrocs were just over and just under 0.5" (12.7mm).

1/2D range would represent rocket speed. The rockets would use solid fuel to accelerate quickly and then use small fins to maintain their trajectory to Max range. In essence, the base damage represents the bullet slamming into the target.

If there's no sustainer motor, they don't have a flat trajectory unless they have actual flight surfaces (and that introduces rather a lot of drag).

[Rupert]

Originally Posted by Fred Brackin

But of course there is no rifling in the barrel because there is no need for a barrel.

You need a barrel to keep the rocket stable and pointed in the right direction until its moving fast enough to be stable on its own. They're also useful for keeping the exhaust out of the firer's eyes.

[Anthony]

Originally Posted by Rupert

You need a barrel to keep the rocket stable and pointed in the right direction until its moving fast enough to be stable on its own.

Though that isn't terribly far. The SMAW is 17 calibers long, almost half of which is the length of the rocket itself.

[evileeyore]

Originally Posted by Anthony

Though that isn't terribly far. The SMAW is 17 calibers long, almost half of which is the length of the rocket itself.

I... I'm not sure caliber was the word you wanted... but I checked and... well... yeah, it is almost 17 calibers long (loaded).

Loaded length: 1,371 mm
Caliber: 83.5 mm
Length/Caliber: 16.51807228915663

[johndallman]

Originally Posted by evileeyore

I... I'm not sure caliber was the word you wanted... but I checked and... well... yeah, it is almost 17 calibers long (loaded).

For artillery, describing barrel length in multiples of the calibre is routine. It gives you an idea of the intended usage of a gun.

[Fred Brackin]

Originally Posted by Rupert

You need a barrel to keep the rocket stable and pointed in the right direction until its moving fast enough to be stable on its own. They're also useful for keeping the exhaust out of the firer's eyes.

The part on the original gyrojet that kept exhaust out of the user's eyes was more like a breach than the ventilated barrel.

That initial "stabilizer" is usually more like alunch rails than a barrel and in this case anthony's 17 calibers is going to be too long for a 15mm pistol. That's part of why I suggest just getting rid of the too inaccurate to be useful unguided gyrocs.

[evileeyore]

Originally Posted by johndallman

For artillery, describing barrel length in multiples of the calibre is routine. It gives you an idea of the intended usage of a gun.

Learn something new every day.

[Varyon]

Originally Posted by Anthony

That's the basic problem with gyrocs anyway; you shouldn't be trying to use rockets to do a job that conventional munitions does just fine, you should be using rockets to do a job that rockets are good at.

Aside from the "kewl" factor, I'd say the advantages of a gyroc would be a) more readily converted to smart munitions than a normal rifle round, b) lightweight firing platform, c) minimal recoil, and d) flat trajectory. The advantage of B is probably lost due to the fact the rounds would probably be heavier than comparable rifle rounds (although this may not be the case if there's some fuel that has greater specific energy than gunfoam or whatever rifles use, but works better for a sustained rocket than a rifle). The advantage of D is that distance to target isn't as important when you don't need to compensate for bullet drop, but ubiquitous rangefinders and HUDs could do away with that advantage as well.

The more gradual acceleration of a gyroc may allow for payloads that the sharp acceleration of a rifle makes unfeasible, but I don't know if there are any useful payloads that this would allow for.

Originally Posted by Fred Brackin

I've never assumed that gyroc rounds are loaded in magazines through the pistol grip. Based both on the size of gyrocs and the way they don't need barrels I've always assumed that they used other arrangements.

The Holdout Gyroc would appear to be simple break open single shot like the flare gun it can be used as (among many other things). The four shot Gyroc Pistol may be nothign more than a slightly larger version of that. Note that both of these are noted as reloading with the (3i) notation indicating that these is no magazine invovled, only loose rounds.

This is an excellent point, and I forgot about the Mauser C96 design (and missed the pistol's 3i) when I considered this in my own thread.

Originally Posted by Fred Brackin

I assume a 15mm diameter but at least a 60mm length giving it a shape like a supersonic rifle bullet. Another reason the pistol grip can not serve as a magazine well.

With a very back-of-the-envelope type of calculation, I figured out a 37.5mm length. That was assuming a lead sphere for payload (which may not be unfair) that ate up 50% of the round's mass, and fairly dense (50% of lead) material for the rest of it. 60mm does sound a bit more feasible.

Originally Posted by Rupert

If you look at UT's gyrocs, they are very light (aside from the LSW, which is oddly heavy), do have low MinST levels, and they all have Rcl 1. The weapon stats are not the problem.

I think the idea here is to convert UT's conventional firearms into gyrocs. So, for example, the Anti-Materiel Rifle could be available in Standard, ETC, or Gyroc. I'm not crazy about this approach, but it could be workable.

Originally Posted by Rupert

gyrojet [...] did spin - spinning is actually quite a common method of stabilising rockets in the real world.

I previously read gyrojets did spin, but then came across some mentions that spinning is bad for rockets, so assumed functional gyrocs wouldn't spin. If spinning does indeed work for rockets, that's a different story.

[AlexanderHowl]

Spinning is a horrible idea for a rocket, though it is better than nothing. If you do not have a counterspining element, rockets will go in the direction of the spin while they thrust (rifles do not have continuous thrust, so spin is an advantage rather than a disadvantage). It was used in primitive rockets, but it was pretty much abandoned in favor of fins when people started figuring out aerodynamics.

[Jack Sawyer]

There have been experiments (Variations on squeezebore I believe) meant to form fin-stabilized projectiles without a sabot:

https://patents.google.com/patent/US3229583

The best source is George Chinn's Machine Guns volume 5 which you can find on Internet Archive: https://archive.org/details/TheMachi...MChinn/page/n3

From page 564 onwards

In February of 1968, an original concept invention disclosure was made by an Aeronutronic employee, Mr. J. F. McCarty, on a technique for forming fins on a projectile as it is propelled through the barrel of a gun.
...
The objective of this program was to evaluate the feasibility of the fin forming technique for launching a 30mm fin formed projectile with a weight of 3500 grains at a muzzle velocity of 3000 feet per second
...
The fin forming concept was evolved principally as a high efficiency means for launching a fin stabilized projectile* Fin stabilized projectiles have inherent performance advantages over spin stabilized projectiles for shaped charge, multiple flechette, and rocket assisted ammunition applications. The fin forming concept was designed to provide increased projectile base area while the projectile is in the gun barrel and to provide a fin stability system for the projectile after it exits the barrel.
...

The fin forming concept employs a conical flange on the projectile which increases the effective base area of the projectile while the projectile is in the gun barrel. The fin flange is progressively formed after firing: first into a large base area cloverleaf shape and then into the final fin launch shape. The flange itself forms the barrel obturator for the projectile as it travels down the barrel. In general, the forming operation is accomplished by means of a series of simple bendings or foldings. Swagging, extruding, or other such operations characterized by large plastic deformation of the metallic flange are avoided.

The book has more detail and pictures, so it's worth a read. Heck it also covers a ton more interesting ideas (folded ammunition, trounds, etc.) in greater detail. There's a ton of novel concepts out there tried literally over decades that fiction never considers if you know where to look.