Oh right was that a different trial than the ACR trials

EmericD said:

We tried that during the mid-80s, a 4 mm bullet with a very long sabot, fired from a 5.56 mm barrel, and it was not a success...

As I said elsewhere. I was thinking something like the Anthena PPI projectile but with gas tight winged out bits that would be crushed into the body by the squeeze bore and then a smoothbore bit near the muzzle to clean up the exterior. Should be simple enough to make a barrel for it with a with a rotary forge hammer. Material would just be steel and copper. More exotic in search of anti armour performance but even the base round should be good enough for soft armour and lower plates. 

On a different note I read that the steyr flechette still had 3000fps at 600m. 

Considering it starts with 4800fps,  that's incredible energy retention.  

I wonder what the retained energy would be like with a conventional. 15 or. 16 cal bullet (which is of course a heavy VLD)

Emeric  do you have the name of that 80s sabot cartridge

smg762 said:

Considering it starts with 4800fps,  that's incredible energy retention.  

4800 to 3000 is about 40% so well within the realm of a VLD projectile. 

smg762 said:

I wonder what the retained energy would be like with a conventional. 15 or. 16 cal bullet (which is of course a heavy VLD)

.16 to .224 is .71% so they will have about .71 the BC.  Very roughly - all other things being the same - BC is linear with SD, and SD is linear with projectile length.

I think to match that retention ratio at 600m you'd need a 338 or higher. 

Unfortunately no one has tested the ranged performance of .17 (or smaller) vlds because anything above 30grain has caused stability problems

A hypothetical. 15 or. 16 bore riding round would need a very long barrel.  Even the. 17 suffers if you go below 24inch

Regarding flechettes,  as well as the long ACR darts,  I've seen much shorter,  thicker,  stumpier darts. 

Almost a bullet with fins.  Could that maybe solve some problems I wonder

With a MV of 4800 fps and 3000 fps at 600 m, that's an energy retention of 39%, which is exceptionnaly good only if you compare it with the 5.56 mm M193 (11%).

Other military rounds are not so bad, for example the 600 m energy retention of the old 8 mm Lebel was 40% when loaded with the Mle1898D bullet, and the 600 m (expected) energy retention of the 6.8 mm NGSW will be higher than 43%.

smg762 said:

Emeric do you have the name of that 80s sabot cartridge

It was the 5.56 mm MSD ("Munition Sans Douille", or caseless for the english speaking audience) that was developped for the FAMAS MSD.

So basically a 7mm or 30cal is required to match that retention.

 I was coming from the perspective of extrem weight savings,  hence me being so impressed with the steyr approach. 

I've always thought the 6. 8 is utter overkill,  when you can make 600m rounds that are half the weight of 556

people forget that a rifle that can ccomfortably handle a 6. 8,  would have to be at least 3. 2kg,  minus all attachments. 

In pursuing range,  they ignored hit probability (via comfortable recoil)

That's interesting.

You put the energy dissipation numbers for small arms in your awesome GPC study, do you happen to have them for the big ones?

You don't seem to understand the issues here.

As far as I know, 25 mm is the lowest caliber to regularly use sabot rounds (https://www.gd-otscanada.com/product/25mm-x-137-ammunition/).

This is a clear indicator that, with current technology, the bang per buck isn't enough to bother with lower calibers, otherwise sabot rounds would already be everywhere.

Lower caliber sabot rounds are either niche ones (like SLAP, which is far from being mainstream) or didn't go beyond the testing process.