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.

Stan, 

SOCOM isn't developing an EPR bullet in 6.5 mm, RDECOM already has as part of the previous SAAC study. It developed EPR bullets in 6 mm, 6.35 mm, 6.5 mm, 6.8 mm and 7 mm. I guess the technical design package would be amiable to any US military organisation that wanted it. My understanding is that SOCOM units deploying with 6.5 and 6 mm weapons have an EPR loading. 

Un-related to the above and thinking back to your 6 mm Optimum; if you were asked to realise a contemporary  today, how would you go about it or change it? 

Guardsman26 said:

SOCOM isn't developing an EPR bullet in 6.5 mm, RDECOM already has as part of the previous SAAC study. It developed EPR bullets in 6 mm, 6.35 mm, 6.5 mm, 6.8 mm and 7 mm. I guess the technical design package would be amiable to any US military organisation that wanted it.

Okay, that seems logical.

Guardsman26 said:

My understanding is that SOCOM units deploying with 6.5 and 6 mm weapons have an EPR loading. 

Very interesting.  A pity we can't get a photo of either EPR bullet.  

Guardsman26 said:

Un-related to the above and thinking back to your 6 mm Optimum; if you were asked to realise a contemporary  today, how would you go about it or change it?

Oh wow.  I figured the 6mm Optimum was a long dead subject, and have given it no thought for years.

When I came up with the idea, it was still the lead-core bullet era.  So an obvious update would be EPR.

Also, I'd assumed that -- as in the past -- completely new rifles and machine guns would be developed.

The current practice seems to be to restrict OAL of candidate cartridges to that of 5.56x45 and 7.62x51.

Since nobody seems interested in making rifles and machine guns for intermediate-length cartridges, perhaps lengthen the 6mm Optimum case and increase COL to 2.80 inches, or shorten the case and reduce COL to 2.26 inches?

“Titanium is much less dense than the steel and copper used in EPR bullets and sectional density is very important to BC“

It is less dense(~40% less then steel) but with EPR construction a couple ideas come to mind:

-Shorten the titanium tip by ~40% to increase the length of the copper slug, resulting in comparable weight to copper/steel EPR 

-Replace copper slug with Bismuth to increase weight to offset titanium weight loss

Either seems easier then trying to match the weight and form factor with a pyrotechnic spotter/tracer, as those compounds are super lightweight.

gatnerd said:

Replace copper slug with Bismuth to increase weight to offset titanium weight loss

That does not seem feasible.  Early in M855A1 development bismuth was used, but had problems that caused a change to copper.

gatnerd said:

Either seems easier then trying to match the weight and form factor with a pyrotechnic spotter/tracer, as those compounds are super lightweight.

M62A1 Tracer weighs the same as M80A1 Ball, which indicates that matching the bullet weights may not be overly difficult.

It seems like it would be difficult to match form factors, considering how different are the shapes of EPR and Tracer bullets.

sorry, my BSmeter went off too loudly for me to watch that