Interesting article about the considerations required for developing the NGSW. It's not just the 6.8 mm that matters.
NATO and the Next Generation Squad Weapon- NGSW » Wavell Room
The article I think focuses on one aspect of the XM7/XM250 selection but not all of them. To its detriment.
First although the Hybrid case is excellent and it enables the M7 to meet its goals.
However It wasn’t the only solution. The Hybrid case offering by Sig was selected as it allowed them to get extremely Spicy performance from a short barrel length and weight reduction required. The NGSW required about a 25% reduction in mass vs equivalent Brass cased ammunition and
Still get about 3000 to 3200 ft/s.
Military Arms Channel YouTube
Please note he is using non AP, GP contract overrun ammunition via a Commercial Sig Spear with a 16 inch barrel so groupings are respective of a combat rifle of 4MOA or better and there is a 3 inch barrel length advantage vs XM7.
This video is him using match grade ammunition and getting superior accuracy but at reduced pressure load and velocity.
Sig’s XM7 and XM250 are doing that with 13 and 17.5 inch barrels respectively. The last surviving competitor until selection was the Lone Star Future weapons/ True Velocity RM277. RM277 had to use a barrel of 19 for the rifle and 22 inches for the AR version in order to get the propellant burn time well keeping the pressure curve down and allowing the high velocity. However to meet the U.S. Army’s NGSW requirements the rifle had to have an overall length similar to the M4 carbine necessitating a bullpup configuration in the RM277 and other longer barrel submissions where conventional submissions had to devise hot loads to “brute Force” there way to the required velocity.
This velocity and in turn increased impact energy is intended for the U.S. Army’s concerns about Armor and cover. Feedback reports from initial units with the XM7 and XM250 the 101st AB and 3rd armored included remarks that highlighted this in description of rounds punching through cinder blocks and 9mm steel plates. With potential that it might be possible for it to Pen BTR, ZSL92 or Tigr light armored vehicles.
So an M4 sized package with AP performance but farther critical here is that the want is extended range AP performance.
The article touches on this aspect that most infantry training and engagement has been focused on battle ranges of less than 300m. Farther that in studies a tremendous drop in infantry units performance is noted beyond 300m. Training is clearly an important issue to be addressed but another is the technical limitations which part of what is not covered by the article.
In NGSW everyone is aware to the two most obvious platforms of the system. The XM7 rifle and the XM250 LMG. All are aware of the 6.8x51mm intermediate rifle cartridge with its hybrid case that is common between the XM7 and XM250. However there are two other common aspects for them. The Muzzle break/Suppressor and the Standardized XM157 LPVO.
“PEO Solder Lethality” said:
The XM157 system is a ruggedized fire control that increases accuracy and lethality for the Close Combat Force. It integrates a number of advanced technologies, including a variable magnification optic, backup etched reticle, laser rangefinder, ballistic calculator, atmospheric sensor suite, compass, Intra-Soldier Wireless, visible and infrared aiming lasers, and a digital display overlay.
This optic allows the Soldier using the M7/M250 a longer range of view and to take advantage of the capability of the 6.8x51mm. Though only with the training and range time. Though with the recent proliferation of laser warning devices to infantry that may require a redesign.