I joined this forum solely to reply to this thread.
I am a recent acquirer of a XCR-M. (.308, 20" light barrel, 3-port muzzle brake, standard upper, M-Lok rail). Ordered in July, received in December. Saw a lot of complaints above about the wait time. That really long cold & flu season did a doozy on supply chain management.
I have put just over 100 rounds through it, entirely 147 gr FMJ. Thus far I have identified one infrequent but persistent malfunction, which is either due to the rifle not being optimally lubricated...or it's the ammo. I do not think it is the magazines, because it has happened with both the steel mags and PMAGs, but I can't rule that out entirely. What is happening is a first-round failure to enter into battery. It is occurring both when I release the bolt from lock-back on a full mag, and when I engage the charging handle. It is not easily noticed audibly or visually, and a trigger pull results in a light primer strike. Clearing the round requires bracing the rifle and pulling back on the charging handle with two hands. I have tried PMC, Armscorp, and Magtech ammo thus far. I am near certain all these malfunctions have happened with the Magtech M80 ball ammo. Only one time has it occurred AFTER firing a round; it's typically right when you load a fresh magazine.
I got into an XCR-M because I'd been researching battle rifles for months, found too many flaws in each of the Cold War Classics, and decided to pick one that, despite not really being "battle proven" drew heavy inspiration from the best of what's out there. So if my accuracy is not sub-MOA, that's ok for me. I have my 6.5 Creedmoor B-14 HMR for that. What I do expect out of this rifle though, for what I paid, is rugged reliability. The rifle seems properly gassed on Setting 4, as there have been zero issues with extraction or ejection (it's really good at chewing up brass; lots of neck crimps).
Shooting with the iron sights it comes with, I've been pleased with the relative accuracy at 25 yards indoors. The recoil is well-managed by the muzzle brake. I plan on getting a flash hider as well just to get an idea of how much recoil is reduced by the brake. It is a heavy platform, but not unbearably so. Mounted with my LPVO (the new Arken EP-8) for a dress rehearsal the setup weighed a bit over 12 lbs.
Getting this out-of-battery issue resolved is my top priority at this point. If any of you XCR owners have had this happen, what did you find was the culprit?