I do not recall seeing the subject ever having been discussed in this forum, nor do I know if 7.62 NATO can chamber and fire in a 6.8 NGSW weapon.  Perhaps someone else knows.

PRM2 said:

From inspection of the cartridge comparison picture, it looks like the action probably wouldn't close if 6.8 was loaded in a 7.62 NATO weapon due to the shoulder position (relying on out of battery safety as well), however would 7.62 NATO chamber and fire in a 6.8 (possibly forced closed with the forward assist) with potentially catastrophic results?

Chambering a 7.62 mm NATO cartridge into a 6.8x51 mm weapon seems as easy as chambering a 7.62 mm NATO into a 7-08, a 260 Remington or a 243 Winchester weapon.

Indeed NGSW 6.8mm for full sized battle rifle like Ar10, FN FAL , SCAR H  kinda nonsense it they really meant to replace any 5.56 arms

The probable mitigation with that list of cartridges, plus 6.5 Creedmoor, is that they are likely to be used by specialists, who would be more likely to catch the potential 'Murphy'. The likelihood of potential miss-chambering would massively increase if 6.8x51 weapons were mixed with 7.62 NATO weapons in more general usage, unless as many people suspect, 6.8x51 ends up being used primarily in the DMR only as a specialised anti-armour round. 

It would be an interesting test to do with a 7.62 NATO drill round, or in the unlikely event of being allowed to potentially write off an expensive new rifle, do a remote test with a live round! 

stancrist said:

I do not recall seeing the subject ever having been discussed in this forum, nor do I know if 7.62 NATO can chamber and fire in a 6.8 NGSW weapon.

With some 7.62 bullets, the bullet would get jammed in the freebore section.  The neck area of the 6.8 NGSW chamber is smaller than the neck on the case of a 7.62 NATO round, 0.312" vs 0.3435".  This  would prevent chambering the 7.62 round even if the 7.62 bullet were pushed back into its case.

PRM2 said:

The probable mitigation with that list of cartridges, plus 6.5 Creedmoor, is that they are likely to be used by specialists, who would be more likely to catch the potential 'Murphy'. The likelihood of potential miss-chambering would massively increase if 6.8x51 weapons were mixed with 7.62 NATO weapons in more general usage, unless as many people suspect, 6.8x51 ends up being used primarily in the DMR only as a specialised anti-armour round. 

Special Forces are already using .300 AAC weapons along 5.56 mm weapons, and we know for sure that some .300 AAC cartridges fit perfectly into 5.56 mm chambers. If you want a problem waiting to happen, then you have it.

You are not going to chamber a 7.62 mm NATO cartridge into a 6.8 mm or a 6.5 mm chamber, but yes, people could be issued the wrong ammo for their rifle.

That is an interesting real life gotcha. I could imagine the following type of event happening:

In close contact with the enemy, mates dead or wounded, ammo running out. Only possible source of ammo is some belted, looks very similar to my 6.8x51, quickly de-link it and stuff into magazines. S**t the action won't close. Is it dirty due to number of rounds fired? No time to check, enemy is almost on me, kick the b*stard closed. Click. Possible outcomes:

1. Have an expensive jammed up club.

2. Keblam, dead or injured soldier.

PRM2 said:

kick the b*stard closed.

Hmm.  How do you plan to kick the bolt closed when the XM7 has no bolt handle like the M14 and no forward assist like the M16?  

Excellent point, however in the future the XM7 may not be the only 6.8x51 weapon (there is already a mock up of an Australian proposed bullpup - I've always liked the the design of the AUG and derivatives as a non-crap bullpup). However it may be that this is used as a good reason to stop people putting unnecessary forward assists on AR15/M16 derivatives!

https://soldiersystems.net/2023/09/21/us-army-begins-fielding-next-generation-squad-weapons/

Having recently completed Production Qualification Testing of the XM7 Rifle and XM250 Automatic Rifle, the US Army has begun issuing the first of the Next Generation Weapon System to A Co, 2-502, 2nd Bde, 101st Airborne Division. Of note, the famed 101st was also the first unit to receive the M17 Modular Handgun System.

To further enhance lethality, NGSW is paired with a new Fire Control System manufactured by Vortex Optics. 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.

The NGSW-FC is the planned replacement for the Close Combat Optic, Rifle Combat Optic, and Machine Gun Optic within the Close Combat Force.

It is important to note that the Army’s position is that Fire Control doesn’t replace training but enhances the fundamentals.

For those of you wondering, the XM157 uses two CR132 batteries and the life is 250 hours on the low setting.