So I haven't even fired round 1 through my rifle yet, but I had a little time last night to give it a wipe down and see how it goes together. My buddy (who owns the M96) is a little curious about the XCR, so I sent him a description of how it worked. I haven't really seen a semi-complete posting of how the weapon generally works here, so I thought I'd share what I sent him, and hopefully it can help some newbies/people who aren't familiar with the weapon. This is what I sent him:
Well I didn't have much time last night, but I wiped down the exterior of the rifle, and did a basic field strip (did not remove the barrel) and wiped down the internals. Have you ever seen the inside of one? It is kind of a cross between an AK and FAL.
Milled upper and lower like an AR/FAL, except with a monolithic/free floated upper of course. The trigger group operationally is very similar to an AR's. But, the trigger parts are *not* the same. It does use some very small AR parts, like the mag catch button, and I think some of the detents might be the same (but not sure about that). And it uses AR pistol grips. The stock interface is proprietary. The mag catch operationally is very much like an AR of course. The bolt catch is a vertical post that goes through the lower directly behind the magwell, that is very similar to that of a FAL. At the bottom though (forward of the trigger) it flares out so the bolt can be released with the trigger finger of either a right or left handed shooter. Nice touch.
The upper and lower "shotgun" open like an AR or FAL. The front is on a captive pivot pin similar to an AR, but the method of retention of the pin is a wire clip instead of a detent.
The recoil spring setup is very much AK... it is captive on a rod, and coils up inside the op-rod. The gun is opened by pressing a tab on the back of the recoil assembly forward, and then tilting the receivers open. This removes a small piece of the rear of the recoil assembly from a recess in the lower, allowing the receiver to pivot open. This allows for the recoil assembly, bolt, carrier, and op-rod/piston to fall out the back of the receiver. Each of these is a separate piece.
The bolt/carrier/op-rod, operationally, are more similar to an AK than anything else, with a few differences. It is a long stroke action like an AK. The carrier is not actually integrated to the oprod. The oprod pushes the carrier via their interface, which is a large lug on the bottom of the oprod which inserts on the carrier. Once they are out of the rifle though, they just fall apart in your hand. The bolt is rotating with three large lugs and an integrated cam pin. Very tough looking bolt, similar to an AK but with one extra lug. The slot in the carrier that engages the "cam pin" goes all the way through to the outside of the carrier... that is a little different from an AK. The extractor is a large piece that looks very AK-like. The ejector is a fixed-type that operates like an AK's. However, it is not integrated with the receiver, and is bolted in. I've yet to decide if I think this setup is a good idea.
The charging handle is on the left side and operates just like that of an FAL (non reciprocating), but it also doubles as a forward assist... you pull it to the rear, then press the knob in toward the receiver and push forward to get the forward assist action. I really wish the FAL had this feature as well. I've always thought the FALs biggest weakness is no forward assist.
The adjustable gas system uses a plug that is very FAL-like: it rotates to a position where it just comes out the front of the gas block. There are several ports in the XCR gas plug to allow for varying levels of gas impingement... so the plug doubles as a regulator. At first glance I think this is superior to the FAL setup that uses the sleeve over the exhaust port as the regulator, with the plug just being an on/off switch. I've heard a few reports of this sleeve failing (breaking) and if that happens you are dumping most of the gas and probably have a rifle that won't cycle since its not getting enough gas. I doubt this could happen with the XCR.
Overall I think its a very well thought out design. Looking forward to shooting it.