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ACR Rifle Trial Results found   Small Arms <20mm

Started 13-Dec by gatnerd; 2170 views.
gatnerd

From: gatnerd

13-Dec

Finally managed to find the ACR rifle trial results. 

You need to go to this website, scroll down to the Bibliography, and click 'ARDEC' which will will take you to the Small Arms Review archive. For some reason it cannot be direct linked:

https://armourersbench.com/2018/03/09/colt-advanced-combat-rifle/

**Edit** I've uploaded the PDF to DocDroid should the above link ever go down:

https://www.docdroid.net/ffL1XVy/s00440-pdf

I've highlighted some of the most interesting aspects.

Info on the 2x types of M16's used for the Baseline:

No practical difference was found between any of the weapons in close range. 

Differences were found in Intermediate Range:

Long Range also showed differences:

Overall summary:

  • Edited 16 December 2020 0:13  by  gatnerd
In reply toRe: msg 1
gatnerd

From: gatnerd

13-Dec

So, I was quite shocked by the results.

I had always assumed that the ACR rifles did better then the M16, but had failed to achieve the unrealistically high "100% improvement over the M16." 

I had figured they probably did 30-50% then the M16 - still a great advance, but not enough to convince the beancounters to shell out the $ for that level of incremental improvement.

Well, that turned out to be totally wrong. The M16 (with and without optic) ended up performing better then any of the ACR rifles.

Not only were the ACRs not a 100% improvement, but pretty much across the board they all ended up measurably worse then the M16. 

The only increase in performance over the M16 with Irons was found at long range...using the M16 with 4x ACOG, as well as the modified Colt with ACOG. 

So, this does help explain the enduring AR forever lifestyle we've found ourselves in. 

  • Edited 13 December 2020 4:51  by  gatnerd
autogun

From: autogun

13-Dec

A good find - and very interesting. I had shared your understanding of the results (better, but not good enough). 

Did you also locate some tests I recall reading about which compared the hit probability of 7.62 mm rifles (including duplex ammo) with 5.56 mm? I seem to recall that the duplex (forget the number - M198?) did rather well.

gatnerd

From: gatnerd

13-Dec

No I didn't find anything on that (I stumbled across the ACR results randomly looking for info on the Colt ACR Aiming Rib).

But there was some mention of duplex performance in the ACR trials:

I kind of skimmed over parts of the document, there may be more Duplex info. 

JPeelen

From: JPeelen

13-Dec

I am afraid the measured hit probabilities are on the high side.

The instrumented range had its long range targets located exclusively at "round" distances: 300, 400, 500 and 600 meters.  Targets on the battlefield will not be exactly at these distances, but somewhere in between. Even if the distance is known to the shooter, sights and reticles are graduated in steps (clicks). So you have to dial the closest sight setting or use hold-off.  

Therefore, bullet impact will nearly always be above or below the line of sight. This reduces the chance of a hit still further. 

I do not think it would have significantly changed the overall outcome of the ACR test. And I also recognize the infrastructural problems on an instrumented range. But in my opinion it is indispensable to have most of the longer range battlefield targets at "in between" distances. In particular when comparing projectiles with very different trajectories.          

gatnerd

From: gatnerd

13-Dec

JPeelen said:

The instrumented range had its long range targets located exclusively at "round" distances: 300, 400, 500 and 600 meters.  Targets on the battlefield will not be exactly at these distances, but somewhere in between. Even if the distance is known to the shooter, sights and reticles are graduated in steps (clicks). So you have to dial the closest sight setting or use hold-off.  

I agree, I'd love to see more ranges set up with weird, unknown target distances (ie 537m, etc.) That is much more realistic - and also why a 'smart optic' would be so useful. 

That said, from my reading of the ACR test, all the targets were short duration, pop up targets, often triggered at random distances. 

So the soldiers would not have had any time to adjust their sights to a given range.

EmericD

From: EmericD

14-Dec

gatnerd said:

Finally managed to find the ACR rifle trial results. 

Thank you very much for sharing the link.

I didn't remembered that the Steyr ACR fired from an open bolt... maybe that could explain the low hit probability above 50 m?

gatnerd

From: gatnerd

14-Dec

I'm happy to have found the link to share; I've been curious about the ACR trials for years, so it was Christmas come early when I stumbled across the PDF.

In terms of the Steyr, it seems to have comparably poor hit probability to the AAI, which seems to indicate that it's likely a flechette problem. Thus ruining my idea for the flechette firing mini MG42...

What surprises me is how poor the hit probability was for the G11 in semi auto, as that's essentially a closed bolt conventional bullet gun with optical sight. Weird that it would be so much worse then the M16.

EmericD

From: EmericD

14-Dec

It seems that the caseless ammo configuration is inducing specific internal ballistic problems, as detailed in the last part of this report.

The weapon accuracy should not be that good, and the free-recoiling configuration in a plastic housing, with a very high scope, probably did not helped keeping the gun zero.

I remembered that during the evaluation of scopes for the FAMAS rifles, the various scopes tested (ACOG, SCROME J4...) were seated so high on the rifle that hit probability was reduced between 0 and 300 m, compared with iron sights.

I also noticed that in the report, it is written that female soldiers achieved different results than male soldiers so ergonomic problems (length of pull for example) could also be suspected, the G11 being very "boxy" and not an effective shape for "pointability".

gatnerd

From: gatnerd

15-Dec

"It seems that the caseless ammo configuration is inducing specific internal ballistic problems, as detailed in the last part of this report"

Ah, I hadn't read the whole report so I missed that. 

I had wondered if somehow by surrounding the entire bullet in burning propellent, it was either deforming the projectile, or partially melting the lead core, and that was throwing off accuracy.  I'll have to read that part of the report to see if that was the case.

Hadn't realized that the HK was also free-recoiling in semi auto. And you're likely right about the height over bore, its massive:

I wonder if the poor accuracy of the ACR rifles (AAI, Steyr, HK) in semi auto also undermined the hit probability of the hyperburst as well?  

Regardless, for years, I had wondered why H&K and Steyr did not bring their weapons to market after the ACR trials, in hopes of securing some other foreign weapon buyer. 

Looking at these results, its clear why. 

  • Edited 15 December 2020 3:01  by  gatnerd
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