EmericD said:

The "ADVAP / 6.8 mm SP" generation of AP ammo seems to deliver pretty extreme capability, just like the "Stiletto" rounds developped in the UK by Ukrainian designers (that worked previously on the Russian 7N27 and 7N39 rounds if I don't mix the names). The M993 was capable of defeating 18 mm of RHA at 100 m. The DM151 is capable of defeating 16 mm of RHA at 200 m, from a shorter barrel. The "6.5 mm SP" for the Hybrid case Creedmoor could defeat 20 mm of RHA at 300+ m, so better performance than a .50 BMG AP round.

That's great info and an incredible increase in performance over M993. 

I imagine they solved the tungsten shattering issue we saw from M993 vs ceramic?

Stiletto had used a very long tungsten penetrator, whereas early pics of the 7.62 ADVAP showed a EPR style construction, where the penetrator is only ~1/2 the length of the bullet. Have they switched to a full length core, or figured out a way to make the base/slug of the ADVAP EPR add to the penetration?

From 2018:

When they originally started work on M855A1, lead-free was the main goal. Then the decision was made since they were working on a new bullet, increase the terminal performance. 

PRM2 said:

Do you think this is where the future of small arms development may actually go, with 6.8x51 giving confidence that it is a practical concept?

I worked in the hypersonic field before, and the mantra was that "hypersonic is the future of aviation, and always will be!", so I won't bet all my money on that, but...

The gains offered by running at much higher chamber Maximum Average Pressure are so significant that SIG, Federal and others are really working hard on this subject.

For the end user, that's the possibility to launch a 140 gr class bullet at 3000 fps from a 6.5 mm Creedmoor weapon, allowing 338 Lapua Magnum hit probability up to 1400 m from a compact, sub 4 kg rifle, or a 102 gr GP at 3550 fps and defeat some significant armor (you have similar gains wih the 5.56 mm or the 7.62 mm NATO).

For the manufacturers, that's the opportunity to replace all existing small arms with variants that could handle the increased pressure, and increase the cost of ammo.

That's a path the Russians started with their 6 mm "Unified", we just need someone to make the first step and others will follow.

EmericD said:

102 gr GP at 3550 fps

What barrel length would this be? And at what pressure?

EmericD said:

For the end user, that's the possibility to launch a 140 gr class bullet at 3000 fps from a 6.5 mm Creedmoor weapon, allowing 338 Lapua Magnum hit probability up to 1400 m from a compact, sub 4 kg rifle, or a 102 gr GP at 3550 fps and defeat some significant armor (you have similar gains wih the 5.56 mm or the 7.62 mm NATO).

These cartidges are pretty powerfull. ME wise in the league of the 7,92x57 or the 30-06.
Frome a 4 kg rifle these would be rather unpleasent to shoot. I am not sure that these would be a sensible choice for general issue. Concidering people compain about the recoil of a 7,62x51 from a 5 kg rifle. Some even concidering it uncontrollable.

This is the root of the problem of small arms development. A human can handle only so much weight and recoil. It also only takes a given amount of damage to kill a human. Since a human can only be killed once there is no use in overkilling. So there are some pretty hard limits to several factors involved. Small arms designes are pretty close to the optimum allready. So there is little that can be done to improve. Concidering the 80-20 rule we are well past the point where significant improvements for sensible amount of resources can be made.
One way is to redefine the optimum to set new parameters. Which IMHO is exactly what they are trying to do with the super hot full power or even more power cartidges. For pretty weak and questionable reasons IMHO.
But this is of course nothing special to the small arms sector.

gatnerd said:

What barrel length would this be? And at what pressure?

I'm not 100% sure because the speaker said 14.5'' and 75,000 psi (which seems much too short), and mixed data from IWs and DMRs, so most probably 18" and 75,000 psi.

schnuersi said:

These cartidges are pretty powerfull. ME wise in the league of the 7,92x57 or the 30-06. Frome a 4 kg rifle these would be rather unpleasent to shoot. I am not sure that these would be a sensible choice for general issue. Concidering people compain about the recoil of a 7,62x51 from a 5 kg rifle. Some even concidering it uncontrollable.

That's right, but a current "4 kg" rifle is supposed now to be strapped with accessories, and those high pressure rounds are going to be used with suppressors that are making a good job in reducing felt recoil (and increases rifle weight). 

A 102 gr (6.6 g) bullet launched at 3550 fps (1082 m/s) is generating only 7.14 N.s of impulse when fired with a suppressor, or only ~60% of the impulse of the 7.62 mm NATO when fired from a '60 era rifle with just a flash hider. 

Or just 20% more than a regular 5.56 mm NATO rifle equipped with a flash hider...

EmericD said:

That's right, but a current "4 kg" rifle is supposed now to be strapped with accessories, and those high pressure rounds are going to be used with suppressors that are making a good job in reducing felt recoil (and increases rifle weight).

True.

But to me it seems that is just going around in circles. One reasons besides the recoil that battle rifles have been replaced has been the high weight of the weapon an ammo. Now even higher weight is lobbied as being positive because it reduces felt recoil.
IMHO that is a case of you can't have the cake and eat it.
Either you want low weapon and ammo weight for easy handling, lots of carried ammo and saving the soldiers endurance because of lower encumberance OR you want a powerfull weapon and accept that it and its ammo will be heavy.

EmericD said:

A 102 gr (6.6 g) bullet launched at 3550 fps (1082 m/s) is generating only 7.14 N.s of impulse when fired with a suppressor, or only ~60% of the impulse of the 7.62 mm NATO when fired from a '60 era rifle with just a flash hider.

which immediatly brings up the question how would a modern 7,62x51 rifle with a suppressor behave. How heavy would it be and is its power sufficient.

EmericD said:

Or just 20% more than a regular 5.56 mm NATO rifle equipped with a flash hider...

...and a 5,56 rifle with a suppressor?

Physics can't be cheated. A heavy load for a soldier 50 years or more ago is a heavy load for a modern soldier.

I also don't really understand what the point of basically issuing DMRs to every rifleman is. To me it seems like a 180° change to what has been preached as the one and only truth in the last 40 years or so. While the heavy load you suggested above certainly would make an intresting MG loading I am not sure that the improvement of 7,62x51 is worth the effort. Especially concodering that the performance of 7,62x51 can be significantly improved by modernising the cartidge.

stancrist said:

Well, what? You said he performed the clearing procedure "just like he was trained to do." Therefore, I can only conclude that he was trained to:    1.  Not care where his gun was pointing.    2.  Not remove the ammunition feed device from the weapon before retracting the bolt to clear the chamber.

Sorry, I was thinking that you were troll joking.

The guy was clearing the gun on top of an armored vehicle, less than 10 minutes after being fired at, the MG pointing to the ground. He checked that the muzzle was pointing in a safe direction but didn't see that someone exited the vehicle, walked around and stand in the LoS, because adrenaline was still pumping high and he was relatively new to the gun, so he focused his attention. That was a first mistake.

He then forget to remove the ammo, which is a second mistake, but I suspect that he had the habit to just unlock the magazine on his rifle before "clearing" it, and re-inserting it after. In this case, he focused on opening the feed trail, checked that the chamber was empty, then close the feed cover just like he closed the bolt on an empty chamber on his IW, then dry fire the gun.

The brain is good to make different things looking similar. You retract the bolt on your IW to see the chamber, just like opening the feed tray on your MG. When you close the bolt on your IW, you no longer see the chamber, just like closing the feed tray mask the chamber on a MG.

So, yes, he made at least two mistakes, and it's fine that accidents happen only when people make several mistakes at once.

stancrist said:

Now you are being quite blatantly dishonest.  I did not say that training is overrated. I said the benefit to training of a "matched pair" of 5.56 and 7.62 rifles is overrated.

Now I was troll joking.

You listed so many different guns (rifles, carbines, SMGs, MGs) of so many different calibers that I doubted that the demonstration was limited to 5.56 mm and 7.62 mm rifles.

schnuersi said:

True. But to me it seems that is just going around in circles. One reasons besides the recoil that battle rifles have been replaced has been the high weight of the weapon an ammo. Now even higher weight is lobbied as being positive because it reduces felt recoil. IMHO that is a case of you can't have the cake and eat it. Either you want low weapon and ammo weight for easy handling, lots of carried ammo and saving the soldiers endurance because of lower encumberance OR you want a powerfull weapon and accept that it and its ammo will be heavy.

I agree, and I'm not advocating to replace the Infantryman IW with a rifle designed around an "Uber cartridge" with a 1200 m effective range, that will need a 1 kg smart scope for good measure.

You can buy a 5.56 mm cartridge for 0.25-0.30 € on the current market, while the future price of the training 6.8 mm is above $2. That's simply not sustainable for a country like France.

But "high pressure" modernization of ammo could also be applied to a diminutive round like the 5.56 mm, like the one Federal is developing (>2100 J from a 20" barrel).

schnuersi said:

I also don't really understand what the point of basically issuing DMRs to every rifleman is.

Neither do I, but I don't have the budget of the US Army neither.