[Legolas]

The US Army appears ready to begin testing a prototype of what might become the next US Military service cartridge. The Army began the search for a new rifle, light machine gun, and new cartridge in 2017, under the program title, Next Generation Squad Weapon (NGSW). Initial competitors were narrowed down to two, Sig and General Dynamics/True Velocity. In April 2022, Army spokesmen announced that Sig had won the competition. Sig will produce prototype rifles and light machine guns chambered in the Sig designed cartridge .277 Sig Fury. Lake City Arsenal is gearing up to produce prototype ammunition in conventional brass cases, but also in a Sig designed hybrid case with stainless steel case head attached to brass case walls. This hybrid case has been approved by SAMMI to operate at 80,000 psi max. Some discussion about this cartridge has already taken place in another thread titled, “Operating Pressures of Modern Bolt Actions.”

I am starting this thread because I would like to hear members opinions on the merits and suitability of this new service cartridge. I am particularly interested to hear from veterans who surely have informed opinions about the strengths and weaknesses of 5.56 and 7.62mm, and what they think we need now.

The .30-06 was our service cartridge through two world wars. The experience of WW2 lead the US military and our NATO allies to search for a more appropriate common service cartridge and rifle. Most here know about the controversies involving the M14 and the FN FAL, and the US imposition of the .308/7.62 on the NATO allies who preferred a moderately powered 7mm or .277 cartridge.

Toward the end of WW2, the Germans developed and fielded the “Sturmgewehr 44” firing a moderately powered and light recoiling 8mm cartridge that proved very effective out to 200 yards and beyond. The Soviets were so impressed that they developed the 7.62 x 39 chambered in the AK 47.

The M16/M4 are light weight rifles, and it is possible for a soldier to carry a 1000 rounds of ammunition, but it is a short range cartridge. The Army thinks we need a long range cartridge that hits harder and penetrates deeper. I would like to hear what members (particularly veterans) think about the .277 Sig Fury, and Sig’s XM5 rifle and XM250 machine gun.

 

[Legolas]

Hornady has a 145 gr ELDX with a ballistic coefficient of 0.536. If the Army has something like that with a steel penetrator tip, it might serve as an economical general purpose bullet. I doubt (don’t know) if that would go through body armor.

Nosler has an Accubond Long Range 150gr bullet with a 0.625 ballistic coefficient, which indicates the long range potential of a .277.

In the original Army specification for the contract competition, they wanted the competitors to develop a cartridge that would use two .277 bullets (135gr and 140gr) which had already been designed at Picatinny Arsenal. At least one of these is presumably something special regarding ability to penetrate body armor. A bullet could be built with a tungsten core, as DarkLord has mentioned, but I think a bullet so expensive might be reserved as a long range penetrator used against fuel and ammunition trucks, rocket launching trucks, radar trucks, aircraft on the ground, etc.. Perhaps a steel penetrator tip with copper clad steel jacket and lead core would serve to deal with body armor, and not break the taxpayers bank. This is just my uninformed speculation. Tdoyka mentioned the black tipped armor piercing, steel core .30-06 bullet used in WW2 (frequently in the BAR). A copper clad steel core bullet would be cheap and probably effective at short to medium range. I think a steel core AP bullet was also loaded in some 7.62 x 51 NATO rounds that would penetrate 1” of steel.

If this cartridge is adopted, several loads will probably be developed, including cheap training rounds.

 

[Legolas]

What if NATO had adopted the 7 x 57 Mauser in the FN FAL? With the FN’s adjustable gas block, NATO could have loaded a moderately powered/light recoiling standard load, AND a high pressure/high velocity/armor piercing load. I think the adjustable gas block had 14 settings, 7 of which were numbered. An appropriate setting could have been marked AP, for the high pressure armor piercing load. Another could have been marked S for the standard low recoil load, with plenty of adjustments left for various states of fouling/lubrication/cold weather conditions.

The FN could have been upgraded in the 1980s with a Picatinny rail upper receiver, and a better trigger. We could have had a made in USA version.

The only bolt action rifles I have had in short actions that I have really liked have been .22-250s. I used to load a 6mm Remington for a nephew, and I liked it better than my .243. At one time, I thought a .257 Robert’s would have been a better coyote rifle than my .243. Hornady had to nip and tuck the 6.5 Creedmoor case to get it to fit in a short action, and people load it hot to get the velocity they want. I know many people like their .308s, but if Winchester had necked down the 8mm Mauser to .30 caliber and called it .308 Winchester—they would like it just a little bit more. I have an AR 10 in .308 that I like, but I would like it more if it was a .308 Winchester/Mauser.

If the .277 Sig case was about 2/10ths of an inch longer (like the 7mm Mauser), the Army would be claiming 3300 fps from an 80,000 psi load in a 20 inch barrel, and we would not be contemplating tungsten or depleted uranium bullets to pierce Chinese body armor.

 

[Legolas]

RED-RIDE 350r, you are correct. Much of the combat in recent decades has been at close quarters. The Sturmgewehr 44 and AK 47 and M4 and M249 SAW have all been effective at close quarters. The use of light weight 5.56mm by US armed forces has allowed them to expend overwhelming amounts of ammunition at close range. We would be giving up something by switching to an ammunition type that weighs 2.5 times as much as 5.56. This is where we need the advice of veterans.

In a previous thread discussing the .277 Sig, “Operating Pressures of Modern Bolt Actions,” member rickyerby said, “ The average squad will have reduced ammo and fire power and more weight. We have based this decision on some pie in the sky 800 meter scenario and surrendered the 0–200 meter battle space that we have dominated. Also far more people are killed in that area than at long range. I base this on my military experience and time in Iraq as a contractor.“

from a 2008 thread, “US Army to continue cartridge search,“ member Chucknbach wrote: “If I was still a SAW gunner in the army I’d be praying to keep it the same. At a 1000 rounds a minute you need to pack a lot of ammo….I’ve read a few of these arguments on having bigger rounds it’s always brought up about knockdown power and one shot one kill theories all fine and dandy arguments. What it doesn’t take into account is suppressive fire. In my training you were doing one of two things advancing or retreating both of which require a lot of rounds to be fired to keep their heads down so your buddy doesn’t get shot while advancing or retreating….”

The question is, what will the battlefields of the future be like? If the Communist Chinese are ever the adversary, their soldiers will be wearing modern body armor and they will be supported by modern naval and air forces. They will have drones and rocket artillery and some satellite surveillance. I think our Army leaders have thought carefully about all this. If the Army leaders think it is important that our soldiers have the ability to overcome an enemy wearing body armor, then we should support our troops with the best equipment possible. I don’t think that means we have to scrap the short range weapons.

Something not mentioned yet are the sighting systems. The Army has been issuing optical sights for years, and in recent years a 1 x 6 power scope has been supplied for the M4. This year a contract was given to Vortex to supply a 1 x 8 scope (made in USA) with an electronic module piggybacked onto it. This module has a laser rangefinder, ballistic calculator interfaced into the reticle, corrected for temperature and barometric pressure, and the ability to calculate trajectory for different ammunition types. I think the contract is for 250,000 scopes over 10 years, and I think they are destined for the M5 rifles and M250 machine guns. Imagine a machine gun burst, precision on target first time. I think the Army is trying to give our troops the equipment they need.

Youtube video: by Vortex Nation episode 220;
Army selects Vortex for Next Generation Squad Weapon

 

[Legolas]

I am sure Darkker is right about the Army not forgetting about the General Dynamics/True Velocity polymer cased technology. The “6.8x51 True Velocity Composite” was SAMMI approved for 65,000 psi. It has different case dimensions from the .277 Sig, but as I understand it, True Velocity has developed a practical polymer case technology. Their design had a little stainless steel in the rim and case head…not as much as the Sig design, but enough to be approved for 65,000 psi.

The General Dynamics rifle had a moving barrel, kind of like an old Browning A5 shotgun or a Browning .50 BMG, where the barrel came back and helped eject the case. I kind of doubt that a conventional bolt and extractor (like the Sig rifle) could PULL the polymer case for reliable extraction…but I don’t really know.

In a desperate wartime national emergency, where copper would be in short supply, polymer case technology is there.

 

[Legolas]

Rickyerby, thanks for speaking up. We get rapped up in expressing our opinions about a new rifle and cartridge, or we should use a classic cartridge, or it’s a waste of taxpayer money to feed the arms industry. Maybe nothing we write on this forum will matter, but we are citizens and we could write our congressional representatives. The tragic stories of the early failures of the M16, where American soldiers were killed because their new weapons jammed, were brought to light when American soldiers wrote to their congressional representatives.

I pray to God that our leaders are blessed with wisdom. I want American soldiers to be well armed and well supplied, and effective at short and long range. During WW2, squads and platoons had a mixture of M1 Garands—M1 carbines—Thompson submachine guns, and ammunition supply had to be complicated. Maybe a squad could have a mix of 5.56 and 6.8 weapons. I don’t know if this would be practical or wise.

Something I have thought about…could drones be used for resupply? Could drones drop off a 200 or 300 or 500 pound package into a hot zone situation?… in a situation where the truck or helicopter was not available? Would you trust your life to that kind of supply line? Could thousands of drones supply scattered small units?

 

[Legolas]

MikeG said, “Why they didn’t gin up this new cartridge on the 6.5mm bore size is beyond me…?”
Many of you have asked this question.

I did some crude calculations trying to get a feel for the ratio of case capacity to bore capacity, and how much force could be applied to the base of bullets in different calibers. Using Pi times radius squared = area of circle (caliber), I calculated for 6mm, 6.5mm and 6.8mm. Using 645.16 sq mm = one sq inch, I converted and calculated pounds of pressure on the bases of the various bullets. A bullet is like a piston in a hydraulic cylinder. The cylinder is like the barrel, and the hydraulic fluid is the high pressure burning gas from gunpowder. The hydraulic fluid applies pressure on the piston (usually 1800 psi in common farm equipment), and the total working pressure is 1800psi X whatever the square inchs on the diameter/caliber face of the piston happens to be.

6mm caliber is 28.26 square mm=0.0438 sq inch
6.5mm is 33.16 square mm=0.0514 sq inch
6.8mm is 36.30 square mm=0.0563 sq inch

6mm-0.0438 sq in X 60,000psi = 2628 # pressure
6.5mm-0.0514 sq in X 60,000psi = 3084 # pressure
6.8mm-0.0536 sq in X 60,000psi = 3378 # pressure
7.62mm-0.0706 sq in X 60,000psi = 4239 # pressure

6.8mm-0.0536 sq in X 80,000psi = 4504 # pressure

So the 6.5mm bullet at 60,000psi will have 3084 lbs of pressure applied to the base of the bullet. A 6.8mm bullet at 80,000psi will have 4504 lbs of pressure applied to the base of the bullet.

The Nosler book shows the following:
.243 Winchester 100gr bullet up to 3100fps
.260 Remington 100gr bullet up to 3300fps
.308 Winchester 110gr bullet up to 3300fps

I think the Army made a compromise. They chose to push for high velocity over aerodynamics and sectional density.
……………………………

I did a little internet searching after the discussion about Sherman tanks and German tanks.

The Sherman’s 75mm gun fired a 20 lb AP shell at 2030fps, a 13.6 lb AP shell at 2850fps, and a 15 lb high explosive shell for infantry support at 1520fps. This gun could destroy all German mark 4 tanks and Stugg 3 armored guns (front facing guns with no turret), and penetrate the side armor of mark 5 Panthers. The mark 4 was mass produced throughout the war and was a peer to the Sherman.

The British 17 pounder “firefly” gun put in some Shermans, fired an AP shell at 2900fps, and a primitive not very accurate discarding sabot round at 3920fps. It may have gotten the name “firefly” because it burned a lot of powder.

The 90mm gun on the US M36 tank destroyers fired a 24 lb AP shell at 2800fps, and the much more effective hi velocity armor piercing (HVAP) 17 lb shell at 3300fps. This gun was very effective against the Tiger tanks.

The German Tiger 1 carried the basic 88mm gun (KW 36) fired a 22 lb shell at 2600fps, and a 16 lb HVAP shell at 3100fps.

The Tiger 2 (King Tiger) had a longer barrel and was chambered for a magnum shell case holding more powder than the standard 88mm KW 36. The King Tiger gun was designated KW 43, and it fired a 16 lb shell at 3700fps. It was designed to destroy large numbers of Soviet tanks.

It seems that with all these guns, the lighter weight/higher velocity shells were the most effective at penetrating armor. I think the Army chose 6.8 over 6.5 because the larger 6.8 bore could PUSH a medium weight shell to effective armor piercing velocity.

 

[Legolas]

In post #74, Tdoyka provided links to two Sig ammunition pages. One is for a high pressure load with a 150gr bullet that looks like a Nosler AccuBond. They claim 2830fps from a 16 in barrel, and 3120fps from a 24 in barrel. So regular .270 Winchester performance from a 16 in, and .270 WSM or Weatherby performance from a 24 in. Sig has an advertisement showing a bolt action chassis type rifle with a suppressor. I think one would need a suppressor or hearing protection to hunt with an 80,000psi cartridge. Ammunition is $80 a box.

Is the suppressor on the M5 and M250 for hearing protection of soldiers, or to hide their position by not giving out raw gunfire noise? If the Chinese are ever the adversary, they will have thermal vision sights and binoculars, and those hot suppressors will look like a big bright bullseye in a Chinese thermal vision sight.

The M250 weighs 16.2 lbs, so about the same weight as M249 SAW, but ammunition will probably weigh 2.5 times as much as 5.56.

The M5 with 16 or 20 inch barrels will weigh close to 9 lbs, with 30 round magazine about 10.5 lbs, and with scope and electronic module about 12.5 lbs at least.

 

[Legolas]

Darkker posted two interesting and historical reports from the department of the Army which I think are worth reviewing. The links can be found in post number 80 from May 15.

The first is titled, “ Operational requirements for an infantry hand weapon,“ or “Study on hit probability of the Garand,”and was published sometime around 1952. It was obviously a U.S. Army research project, but appears to have been done with the assistance of Johns Hopkins University. It begins by commenting on the effectiveness of U.S. Army service weapons from World War II and Korea, and begins to speculate about what type of weapon would be more effective and give the soldier a higher probability of making hits against an enemy.

Initial observations are that terrain and visibility limit a soldier’s ability to fire at an enemy, and that most soldiers have a hard time seeing an enemy beyond 300 yards and therefore do not fire much beyond 300 yards. Soldiers reported that 80% of EFFECTIVE rifle and light machine gun fire took place at less than 200 yds, and that 90% of such fire took place at less than 300 yds. 87% of Korean vets reported that 95% of their rifle fire was within 300 yds.

It was stated that the M1 .30-06 rifle had an effective range of 1200 yds. It was stated the hit probability for the average rifleman declined rapidly past 100 yds, and that hit probability for an expert rifleman declined past 200 yds to a low probability at 300 yds. The hit probability for all riflemen declined under extreme combat conditions.

Regarding the full auto rifles available in 1950 (presumably the M14), it was stated that in 5 round burst testing, only the 1st round would hit the test target at 100 yds because of excessive recoil. Multiple hits could be achieved at less than 50 yds. Regardless of skill or marksmanship, only the 1st round of a burst could be directed to a target at 100 yds. It was stated that, “The fully auto feature was valueless from the standpoint of increasing the number of targets hit when aiming at separated man-sized targets.”

At this point, they began to speculate about the hit probability of low-recoil small caliber weapons. It was stated that, “If the combined weight of weapon and ammunition is held constant at 15 pounds, the overall expected number of kills from a .21 caliber rifle is approximately 2.5 times that of the present standard .30 caliber rifle. It was said that a .21 cal missile at 3500 fps muzzle velocity would create equal damage to a .30 cal bullet at 800 yds. It was also stated that, “Since the recoil of a small caliber weapon would be less than the recoil of present weapons, the dispersion of rounds in a short full-auto burst would be considerably less than the dispersion of current models.”

It was therefore postulated that, “Since 70% of ranges over which a man-sized target is visible to a defending rifleman lie within 300 yds…the short-range weapon will be designed…for maximum effect up to 300 yds…It may be suggested that 7 in every 10 infantry hand weapons should have the characteristics desirable for short-range use.” It was also stated that, “From experience at Fort Benning, the development of no more than two expert riflemen per squad may be expected from the normal recruit stream without special training…This does not mean that it would not be desirable to have much higher performance in marksmanship among all the men in the squad.” The men writing this could perhaps could not even dream of a computerized laser range-finding, trajectory-calculating, intrasquad Bluetooth-communicating, multi-range reticle variable power scope mounted on a Picatinny rail…part of a squad linked to an overhead drone scanning in multiple spectrums (including infrared) and AI processing for suspicious pattern recognitions.

At this point, the researchers speculated that light-weight low-recoil weapons firing multi-projectile flechette ammunition in full-auto low-dispersion bursts could potentially have a much higher hit probability than current weapons. This seemed to be a primary focus of the second research project which Darkker provided a link to, titled “Study on hit probability of the M16 family with optics.” I will try to provide a review of that document in the coming days.