stancrist said:

not developing both EPR and Tracer rounds

I wonder if they will be using tracer rounds? Due to their overwhelming preference for night fighting using night vision technologies, I could see them not wanting their LMG's to essentially look like roman candles. 

They apparently were working on some sort of 'spotting bullet' to replace tracers, although I haven't heard anything since:

https://www.thefirearmblog.com/blog/2019/09/20/socom-looks-for-spotting-bullets-for-replacing-tracers/

USSOCOM is seeking 7.62mm x 51 NATO spotting rounds to replace tracers for adjusting machine gun fire, both day and night, producing a flash and /or smoke signature visible at 800m-1200m. Current tracers allow gunners to observe the trajectory of the rounds and make aiming corrections without observing the impact of the rounds fired and without using the sights of the weapon. However, these rounds give away the gunners position, burn out before the maximum range of the machine gun and draws enemy fire. Replacing tracers with marking or spotting pyrotechnic rounds enables the gunner to directly control the impact on to the target, shows target coverage, and does not disclose the shooters location.

..

One option is the use of 'flash tip' bullets, which are somewhat similar to EPR, but instead of steel have a Titanium tip that sparks on impact. 

6.5 119gr Flash Tip by Lehigh:

They work very well against steel or presumably concrete targets; when hitting dirt they seem to spark but much less significantly. 

https://youtu.be/0wy7fCUiZi4?t=124

Visibility is meh vs tracers, but would allow running a very similar projectile to EPR, and would remove the shooter position revealingness of tracers. 

A dedicated explosive spotting bullet would no doubt be more visible, but like a tracer would be pretty different in shape and weight to a EPR. 

gatnerd said:

I wonder if they will be using tracer rounds?

They apparently were working on some sort of 'spotting bullet' to replace tracers...

The fact that SOCOM was seeking spotting rounds "to replace" tracers indicates that they have been using tracer ammo, at least up to 2019.

Yes, if they can get 6.5 CM spotting rounds that provide acceptable visibility, I agree that SOCOM would probably replace tracers with spotters.

In that event, it just means that instead of developing 6.5mm EPR and Tracer ammo, they would be developing 6.5mm EPR and Spotter ammo.

stancrist said:

The fact that SOCOM was seeking spotting rounds "to replace" tracers indicates that they have been using tracer ammo, at least up to 2019.

That is a good point. 

Although alternatively they could have stopped using tracers, felt their absence, and are now looking for some sort of replacement for that lost capability. 

Whats interesting is in a quick 5 minute glance at youtube of m240 videos from Afghnistan in daylight with regular army, they dont seem to be using tracers?

https://www.youtube.com/watch?v=8xdj0lBklvM

https://www.youtube.com/watch?v=yRPCNUzkqXk

That M249 video where he hoses the entire horizon with 800+ rounds didnt show travers either as I recall.

Unless they're firing some sort of IR visible only tracer. 

gatnerd said:

One option is the use of 'flash tip' bullets, which are somewhat similar to EPR, but instead of steel have a Titanium tip that sparks on impact. 

gatnerd said:

A dedicated explosive spotting bullet would no doubt be more visible, but like a tracer would be pretty different in shape and weight to a EPR. 

Titanium is much less dense than the steel and copper used in EPR bullets and sectional density is very important to BC.  My point is that IF a spotter or tracer is important for aiming, it is likely that the trajectory of the spotting/tracer bullet will be the limiting factor.  This is a bigger issue when a very sleek bullet is desired for improved performance at long range.  Cartridges like 5.6 Creedmoor and 6mm ARC are attractive largely because the civilian versions use high-bc bullets.

Tracer with burning trace hence already hollow tail and burning- reducing mass is already something that is flying in general vicinity , but were not there some plans to make sort of glowing insert that doesn't burn , i would imagine there are materials that could use the heat or pressure generated on firing to glow for 1-1.5 second long

One-Way Luminescence.  Not much heard since ~2016 but it still seems to be a program of record.

https://www.thefirearmblog.com/blog/2016/03/06/one-technology-change-small-arms-game-owl-tracers/

No there won't be an issue because part of the lake city upgrade is setting up high volume one way luminescent tracer lines.

OWL's at least somewhat Change the tracer game

I don't have the article handy but part of the 100 million dollar lake city plant update is for an OWL tracer line.

gatnerd said:

Although alternatively they could have stopped using tracers, felt their absence, and are now looking for some sort of replacement for that lost capability. 

Yes, they could have stopped using tracers long before 2019.

gatnerd said:

Whats interesting is in a quick 5 minute glance at youtube of m240 videos from Afghnistan in daylight with regular army, they dont seem to be using tracers?

https://www.youtube.com/watch?v=8xdj0lBklvM

That certainly appears to be 100% Ball ammo in the close-up views of the belt.

Here's a Mk48 video with linked ammo from can marked M80 Ball.  No Tracer.

https://youtu.be/llEWrL9ghyg?t=85

nincomp said:

My point is that IF a spotter or tracer is important for aiming, it is likely that the trajectory of the spotting/tracer bullet will be the limiting factor.

What you seem to be concerned about might be the case if the spotter/tracer bullet were to be designed first, then the ball projectile developed -- and "dumbed down" -- to achieve a trajectory match. 

But, if Nick is correct that SOCOM is developing a 6.5 EPR bullet first, then a companion 6.5 spotter or tracer will just have to be designed to match the EPR trajectory as closely as feasible.

Edit:  But, since Nick says that SOCOM is already using an existing 6.5 EPR bullet, then a companion 6.5 spotter or tracer will just have to be designed to match the EPR trajectory as closely as feasible.