Auto Rifles and ACRs in vacum

[batmagoo]

If auto rifles use a mettalic case for thier cartridges, and ACRs are caseless, how would an ACR operate in vacum?
A mettalic case would have oxygen and fuel, while the primer would provide heat.
Wheres the O2 for a caseless round?

Chuck

 

[Jame]

I asked this question over on the GURPS free forums. According to LKW, at least, most weapons can, something about their carrying their own O2 supply (being self-oxygenating). Maybe a caseless round does that?

 

[Anthony]

With the exception of fuel-air explosives, all explosives (propellants are low explosives) contain their own oxidizers and do not need an external O2 supply. This includes caseless rounds.

Guns might fail to fire in vacuum for other reasons, however, such as problems with lubrication or sparking. Vacuum is not terribly good for devices which aren't designed for it.

 

[far-trader]

Yes, gunpowder, even the older type, will burn in vacuum and even underwater. It includes an oxidizer in the mixture. The same will be true for a caseless round. It's really not much different than a solid rocket fueled engine (except in performance). The fuel and oxidizer are mixed to an ideal balance and you don't need to worry about the outside environment.

So yep you can use most weapons in vacuum, though there may be other issues to worry about. There are a few older threads on these boards covering these points. Just do a search when you have the time. Use "vacuum" (spelling counts ) and "gun" in the "Search Words" box and "288" in the "Member Number or Public Display Name" box. That's my number and I know I posted to some if not all of them and the search terms should narrow it down some. Search tip of the day. Search by forum one at a time. It's quicker than search by all forums (or seems so).

There will of course be other issues with firing a gun underwater as the ballistics for the two mediums (air and liquid) are very different.

 

[Fritz_Brown]

Originally posted by far-trader:
There will of course be other issues with firing a gun underwater as the ballistics for the two mediums (air and liquid) are very different.

Not to mention the incompressibility of water. The poor bullet has to push all that water out the end of the barrel....

 

[Fritz_Brown]

Here are two results just from Ship's Locker:
AutoPistol in a Vacuum...
AutoPistol in a Vacuum... (A quick bit on handling it in game terms.)

 

[Fritz_Brown]

Dan,
Your search criteria only returned the post above.

 

[far-trader]

Originally posted by Fritz88:
Dan,
Your search criteria only returned the post above.

Hmm, odd. At least it did return that much

I'll have a go and see what I find, maybe that was too specific?

A couple quick searches and yep that's all I find too. It does seem to cover it ok but I was sure there were more times this came up. Maybe it was on the TML or somewhere else?

 

[tucker2]

Is it canon or assumed that ACRs have caseless rounds?

 

[far-trader]

I'd say it's an option

Really the whole ammunition thing should probably be a bit more complex than it's made out in the game, key point being it's a game so it's fine to presume most of the time buying rounds for your Regina manufacture ACR on some backwater world on the rim is no problem

 

[tucker2]

Reason I ask is that in Mercenary, you could shoot mags from assault rifles through your trusty ACR, had some blurb about how you used asault rifle DMs or some such. For my players it made it possible to afford ammo-- early on.

 

[far-trader]

Some guns are able to use a range of similar sized rounds so that seems pretty reasonable.

 

[Fritz_Brown]

I don't think there's much likelihood of caseless rounds working in a weapon that fires normal brass, or vice versa. The mechanisms are different (extractors, the piece that strips the next round out of the mag, etc.) - not to mention the caseless mags are going to be sealed affairs - very unlike normal assault rifle mags.

Of course, that's not TU, that's RL.

 

[Andrew Boulton]

Couldn't you make caseless rounds that were the same shape as cased, and so would work in a standard gun? (Dunno why you'd want to, but it might work).

 

[Fritz_Brown]

I would think the force of stripping them out of the magazine might cause problems (chipping them, etc.).

You also have the problem of the breech shape on a normal rifle. It is designed as a cone, so the bullet will feed better. With a brass cartridge, it actually sits partway in that cone, but doesn't fill it up (going outwards, that is). But, the gas expansion is contained within the brass (and pushed forward), so there isn't a problem. With a caseless round, you would get expansion into that cone, ruining the gas expansion slightly, and opening the breech before the bullet is out the muzzle (further ruining the gas expansion).

(Quick, where did all our gunsmiths go?! Help me out here....)

 

[Uncle Bob]

Breach obturation. The main function of the brass case is sealing up the little gaps in the breach mechanism where hot gases bust out. Caseless round can't do this, so you get hot gases venting into the reciever, damaging the mechanism and maybe the shooter (especially in a bullpup).

 

[Uncle Bob]

Assault rifle has a 6mm bore, the ACR 9mm. You cannot use assault rifle ammo in an ACR. Book 4 does not say if the ACR uses caseless ammo.

Striker added a 9mm slug to the ACR ammo choices. One of my characters had a hunting rifle made up for a .356 Express cartridge that just happened to be dimensionally the same as 9mm ACR ammo. Usually displayed with a 5 rd magazine loaded with hunting soft points to be law-level 5 legal, it would take regular ACR mags if the feces struck the impeller. Easier to hide a magazine of DS than a whole ACR.

 

[mike wightman]

Originally posted by tucker2:
Reason I ask is that in Mercenary, you could shoot mags from assault rifles through your trusty ACR, had some blurb about how you used asault rifle DMs or some such. For my players it made it possible to afford ammo-- early on.

Emm, LBB4 doesn't say that ACRs can use AR mags/ammo.
It says that locals often produce slug rounds for the ACR which should be treated as AR rounds on the weapon matrices.
Note that this would be a 9mm slug

 

[tucker2]

Originally posted by Fritz88:
I don't think there's much likelihood of caseless rounds working in a weapon that fires normal brass, or vice versa. The mechanisms are different (extractors, the piece that strips the next round out of the mag, etc.) - not to mention the caseless mags are going to be sealed affairs - very unlike normal assault rifle mags.

Of course, that's not TU, that's RL.

I get that bit, caseless rounds are a cake of propellant around a bullet. I just didn't ever assume caseless rounds for ACRs, never really thought about it 'til I got on this thread.

In LBB4 do they go into bullet size for ACRs? My book is packed up a the moment, and memory ain't serving.

 

[Andrew Boulton]

"Advanced Combat Rifle: A progressive development of the assault rifle, the advanced combat rifle (ACR) fires either a 9mm, 5 gram high explosive (HE) bullet at 900 meters per second, or a 9/6mm, 3 gram discarding sabot (DS) bullet at 1200 meters per second. A magazine containing 20 rounds is inserted into the underside of the weapon behind the pistol grip.
...
Standard equipment includes an electronic battlefield sight, incorporating both light
amplification and passive IR, visual magnification, and a laser rangefinder which may also be used as a target painting device. The weapon is also gyroscopically stabilized during firing. A sling is provided, and the muzzle of the rifle includes an integral flash suppressor and adaptor for launching a 40mm RAM shoot-through grenade."