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Steyr ACR (Advanced Combat Rifle)

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Donald McKelvy
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The Steyr ACR (Advanced Combat Rifle) was a prototype flechette-firing assault rifle built for the US Army's Advanced Combat Rifle program of 1989/90. Although the Steyr design proved effective, as did most of the weapons submitted, the entire ACR program ended with none of the entrants achieving performance 100% better than the M16A2, the baseline for a successful ACR weapon. The Steyr ACR had a bullpup design like the Steyr AUG, which it slightly resembles.
http://en.wikipedia.org/wiki/Steyr_ACR
http://www.steyr-aug.com/acr2002.htm
http://world.guns.ru/assault/as56-e.htm
http://en.wikipedia.org/wiki/Advanced_Combat_Rifle
 

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Firefly 2

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Bu Jove, I'm absolutely in love ... Never heard of this design before, love it, thanks.
 

Boxman

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1991 video recently posted by Nuclear Vault on YouTube demonstrating the Advanced Combat Rifle (ACR) designs from AAI, Colt, H&K, and Steyr.
Nuclear Vault - Advanced Combat Rifle (1991) - youTube
http://www.youtube.com/watch?v=WpkAPo7DqkY
 

cluttonfred

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That video is a great find, Boxman, thanks for posting. It really shows the differences between the various designs -- that H&K looks like it kicked like a mule in burst fire since it was saving up the recoil from three successive shots. I suspect that it would have come down to a choice between the Colt and the Steyr and the Colt would have won as an American product and because of the U.S. Army's conservatism and desire to maintain compatibility with existing ammunition stocks. On the other hand, it's interesting to speculate what would have happened if there had first been a decision on the ammunition system and then all the competitors were allowed to refine/modify their designs to suit that ammo. A simplified Steyr ACR firing the Colt's 5.56 duplex ammunition might have been a winner.
 

Abraham Gubler

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Steyr performed very poorly because the flechette couldn't remain stable in flight. Look up the G11 and ACR file here and you can see the combat accuracy results I have uploaded.
 

cluttonfred

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Do you mean this post, AG?

http://www.secretprojects.co.uk/forum/index.php/topic,9199.msg97359.html#msg97359

In it, you highlight the hidden bias in equipping the American competitors with more powerful magnification than the European ones. That, combined with the ammunition issues, really made it an apples to oranges competition. It would have made a lot more sense to settle on one a single ammunition type first, provide specs and test ammo to the gunmakers, and then let them all come up with the best gun for that ammo. If you want an optical sight, then make that stage three.

And I stand by my comment that the G11 looks like an absolute b!@#$ to shoot in that video. ;-)
 

Rickshaw

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cluttonfred said:
Do you mean this post, AG?

http://www.secretprojects.co.uk/forum/index.php/topic,9199.msg97359.html#msg97359

In it, you highlight the hidden bias in equipping the American competitors with more powerful magnification than the European ones. That, combined with the ammunition issues, really made it an apples to oranges competition. It would have made a lot more sense to settle on one a single ammunition type first, provide specs and test ammo to the gunmakers, and then let them all come up with the best gun for that ammo. If you want an optical sight, then make that stage three.

One shouldn't assume conspiracy when a cock-up is usually a sufficient explanation. AIUI, the competition rules didn't set standards for any weapon's configuration. Each manufacturer responded AIUI with what they considered was appropriate for the competition.

Your path would have been more sensible if research had been undertaken for what sort of ammunition was the way ahead. However, this was rather a "blue-sky" competition, with little being specified.

And I stand by my comment that the G11 looks like an absolute b!@#$ to shoot in that video. ;-)

It doesn't look like it's recoil is insurmountable to me. Stronger than a single shot but that is expected with three rounds being fired.
 

TomS

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And the whole point of the G11 mechanism is that the burst RoF is very high (~2000 rpm) and the recoil is delayed so that all three rounds in a burst are out of the barrel before the gun moves significantly. In full-auto, the rate drops to around 600 rpm, which is still on the high side, but combined with the very low impulse of each round would be totally manageable.
 

jsport

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TomS said:
And the whole point of the G11 mechanism is that the burst RoF is very high (~2000 rpm) and the recoil is delayed so that all three rounds in a burst are out of the barrel before the gun moves significantly. In full-auto, the rate drops to around 600 rpm, which is still on the high side, but combined with the very low impulse of each round would be totally manageable.

Recall hearing that the G-11s drawback was the caseless ammo "brick". If were cracked, broken or wet some high number of rounds ~50 would be rendered useless.
 

Tony Williams

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cluttonfred said:
A simplified Steyr ACR firing the Colt's 5.56 duplex ammunition might have been a winner.

The problem is that like the current LSAT cased-telescoped round, the gun mechanism was designed around a cylindrical cartridge. I doubt that it could have been adapted to work with a round of conventional shape, like the 5.56mm. These are the four rounds concerned in the ACR trials, from my collection:



The ACR rounds: Colt 5.56mm Duplex, AAI 5.56mm flechette, Steyr flechette, HK 4.7mm G11
 

Rickshaw

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jsport said:
TomS said:
And the whole point of the G11 mechanism is that the burst RoF is very high (~2000 rpm) and the recoil is delayed so that all three rounds in a burst are out of the barrel before the gun moves significantly. In full-auto, the rate drops to around 600 rpm, which is still on the high side, but combined with the very low impulse of each round would be totally manageable.

Recall hearing that the G-11s drawback was the caseless ammo "brick". If were cracked, broken or wet some high number of rounds ~50 would be rendered useless.

Caseless ammunition has many drawbacks against it's use in the field. The cases of normal rounds isolate and protect each round quite well. The price that is paid is weight.
 

Abraham Gubler

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jsport said:
TomS said:
And the whole point of the G11 mechanism is that the burst RoF is very high (~2000 rpm) and the recoil is delayed so that all three rounds in a burst are out of the barrel before the gun moves significantly. In full-auto, the rate drops to around 600 rpm, which is still on the high side, but combined with the very low impulse of each round would be totally manageable.

Recall hearing that the G-11s drawback was the caseless ammo "brick". If were cracked, broken or wet some high number of rounds ~50 would be rendered useless.

Its not an actual brick. It just looks like one. Each round is independent so any damage to one round just results in a loading jam or misfire as in a conventional cased round. The caseless ammo was never meant to or needed to be individually handled. Ammunition was supplied in 15-round stripper clips that were fully enclosed by impact resistant plastic. These clips were then used to load the magazine which was then loaded into the weapon (sounds like a step that could be removed there). So the only time a round would be outside these containers is if you ejected it from the breech to make safe the weapon. In which case it might get damaged and be unusable or soldiers could be provided with a container to put such loose rounds into for later consolidation into a clip or magazine.
 

Abraham Gubler

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cluttonfred said:
In it, you highlight the hidden bias in equipping the American competitors with more powerful magnification than the European ones. That, combined with the ammunition issues, really made it an apples to oranges competition. It would have made a lot more sense to settle on one a single ammunition type first, provide specs and test ammo to the gunmakers, and then let them all come up with the best gun for that ammo. If you want an optical sight, then make that stage three.

If you look at the data in the table it shows the accuracy performance of each weapon. The two flechette firing rifles perform way below the others. That being said I think the Steyr ACR is one of the nicest weapons ever designed. Just a shame about the projectile. But reconfig it for a slug firing round and it would be ideal. Almost like the Great White Whale of the ACR program which was the ARES entry. Which not only used low weight CTA design but also dispensed with the salvo concept as a way of achieving hits and replaced it with a far more sensible adjust fire approach. Shame it was dropped as a cost cutting measure before the trial. But that's another post that I should get around too one day.

cluttonfred said:
And I stand by my comment that the G11 looks like an absolute b!@#$ to shoot in that video. ;-)

There is a reason there is a big rubber sponge guard on the end of the optic sight. But I don't think the actual force imparted into the shoulder would be too bad. Consulting my Williams ("Assault Rifle", and kudos, kudos) the combined recoil impulse of three 4.7mm rounds should be 84 ratio units compared to 142 units for a single 7.62x51mm (1:1.7). The weapon surely bucks after the three round salvo is away but this might be more to do with it being optimised to get the serial burst out of the barrel before the weapon recoils rather than keeping said movement steady in the hands of the firer (like most rifles).
 

jsport

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Abraham Gubler said:
jsport said:
TomS said:
And the whole point of the G11 mechanism is that the burst RoF is very high (~2000 rpm) and the recoil is delayed so that all three rounds in a burst are out of the barrel before the gun moves significantly. In full-auto, the rate drops to around 600 rpm, which is still on the high side, but combined with the very low impulse of each round would be totally manageable.

Recall hearing that the G-11s drawback was the caseless ammo "brick". If were cracked, broken or wet some high number of rounds ~50 would be rendered useless.

Its not an actual brick. It just looks like one. Each round is independent so any damage to one round just results in a loading jam or misfire as in a conventional cased round. The caseless ammo was never meant to or needed to be individually handled. Ammunition was supplied in 15-round stripper clips that were fully enclosed by impact resistant plastic. These clips were then used to load the magazine which was then loaded into the weapon (sounds like a step that could be removed there). So the only time a round would be outside these containers is if you ejected it from the breech to make safe the weapon. In which case it might get damaged and be unusable or soldiers could be provided with a container to put such loose rounds into for later consolidation into a clip or magazine.
Brick was bad word. Thank you for the explaination. Source was the curator, or former at Aberdeen MD Museum.
 

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