While I’m not going to defend the US Army’s terrible ongoing track record in small arms acquisition, I do think that Dr. Orr has either missed the point or is eliding it because he thinks everyone reading Army Times already understands.
Mud Test: If you watch inRange TV regularly, you will find that many many rifles fail the mud test, including some with good reputations. eg. The famous M-1 Garand rifle does terribly when immersed in mud. Is it good that the M-5 fails? No, but how important that is depends on the planned usage conditions.
Armor piercing: The military justification of the XM-5 program is to remedy issues where the standard 5.56 rifles had insufficient range and penetration. Afghanistan isn’t the Fulda Gap isn’t Vietnam and it is a pretty terrible feeling not being able to return fire to some Afghani hobo who is shooting a .303 SMLE and is out ranging you. While 5.56 Armor Penetrating (AP) rounds will go through armor, what he leaves out is this is at much shorter range than the higher power systems and the point of the program was to increase the range. If you actually watch the video Dr. Orr linked, you’ll see that the shot did great damage to the level 4 plate, and the second shot went easily though it. Without an AP projectile, that isn’t terrible.
Rifle gas: As is common, the suppressor is the cause of the rifle gas issue. The included suppressor was also added to make it less detectable and manage the recoil. This also can have the effect of making Direct Impingement (DI) actions (such as in the AR-15/M-16/M-4 series) run very dirty which can cause reliability issues and require frequent cleaning. So the vendors designed rifles without DI actions.
Engineering is all about trade-offs. It is easy to show something is bad, by just showing all the bad things and none of the good. It is easy to show something is good, by just showing all of the good things and none of the bad. Far too much of what passes for discussion these days (here and elsewhere) takes one of the two preceding forms, to our general detriment.
You can make an argument that the 7.62 NATO systems are sufficient for AP at range, but then you end up with the inability to carry lots of ammunition and the limitations of 1950s ammo design. The NG program was trying an intermediate position, with a round between in physical dimension between 5.56 and 7.62, with better weight/volume characteristics, juiced up with a substantial powder charge and an optic that should help reduce ammunition expenditure. It wasn’t a dumb idea for a program, especially considering the earliest versions of the current rifle are now old enough to be eligible for the BATF Curios and Relics licensing. I personally think that once the dust settles it probably isn’t going to replace the current rifle at all levels, but it can certainly be used in some roles with great effectiveness.
Another video from inRange TV, tear down and discussion:
A more evenhanded look at the M-5 by Ian at Forgotten Weapons:
Ian takes the Spear to a shooting competition:
Garand Thumb:
Garand Thumb looks at the Spear LT that shoots 5.56, he talk a lot about he trade-offs involved:
Edit: clear up AP abbreviation, fix punctuation