This is intended for people interested in the subject of military guns and their ammunition, with emphasis on automatic weapons.
Latest 13:09 by stancrist
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Latest 29-Aug by EmericD
Nice, I love their posters.
Watching this interview on SIG's 6.8 ammo:
-Cases currently running "mid 70's" pressure aka around 75kpsi
-Claim the cases can be run to 120kpsi should the future require it
Man, thats worse than what I said.
Gotta love SIG.
I agree with Emeric. A standard pressure 6.8x51 mm NGSW must be VERY close in performance to 6.5 x 49 mm Creedmoor. I believe SOCOM has its own 6.5 mm EPR-style projectile that is identical to the 6.8 mm NGSW projectile in terms of profile, but weighs less - 6-7 grams. A 6.5x49 mm CM fired at standard pressure (55,000-60,000 psi) has the advantage of weighing 18-19 grams versus SIG's 6.8x51 mm cartridge at 21-22 grams. You can also use the 6.5 CM lower chamber pressure to engineer a polymer case to deliver a lower weight cartridge, close to 16 grams.
Emeric, I am not a ballistician, but what do you estimate would be the chamber pressure of a 6-7 gram 6.5 mm bullet fired from a 6.5x49 mm Creedmoor cartridge at 3,000 fps / 914 mps?
Second pint, popped primers with FN SCAR are due to some manufacturers using soft metal primers, not military spec ones. SCAR is designed to meet very demanding military standards. It is designed to achieve 1 mm of penetration for military spec 7.62 mm and 5.56 mm cartridge primers. With soft primers it is achieving 1.5 mm or 2 mm. The latter is obviously too much. I know this, because I was on the range with FN today, and asked their technical lead. (I was firing Evolys in5.56 mm and 7.62 mm ).
I agree with Emeric. A standard pressure 6.8x51 mm NGSW must be VERY close in performance to 6.5 x 49 mm Creedmoor. I believe SOCOM has its own 6.5 mm EPR-style projectile...
Upon what do you base that belief? Emeric said that SOCOM does not use EPR projectiles.
I believe SOCOM is experimenting with EPR projectiles.
That does not answer my question, but I would be extremely surprised if SOCOM is not developing both EPR and Tracer rounds, as they will be needed for the 6.5 CM LMG.
I wonder if there will be issues with developing a tracer that will match the trajectory of the high-BC bullets normally used in the 6.5 Creedmoor (and 6mm ARC, for that matter). It may be easier to match the trajectory of less-dense EPR bullets than to match lead-cored ones.
It has occurred to me that the mediocre BC of bullets used in cartridges like the 280 British and 6mm SAW might have had more to do with limitations of tracer rounds than ball ammo.
I wonder if there will be issues with developing a tracer that will match the trajectory of the high-BC bullets normally used in the 6.5 Creedmoor...
Good question. Perhaps it just requires experimenting with bullet weight and muzzle velocity?
7.62mm M80A1 Ball and M62A1 Tracer reportedly both weigh 130 grains.
5.56mm M855A1 Ball is 62gr, but M856A1 Tracer is much lighter, at 56gr.
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:
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.
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.