Here it is, getting acquainted with some others in the gun safe.

Took it to the range, yesterday. It certainly prefers heavier loads; 55-grain FMJ's reliably short-cycled (with the exception of Remington UMC, which only jammed toward the end of the session). To be more specific, in all cases the spent casing would eject. But with cheap steel-cased (coated with zinc) 55gr. loads the bolt apparently didn't go back far enough to pick up the next one. With slightly more expensive steel-cased 62gr. (coated with brass), the bolt picked the cartridge up somehow from the middle of the case, driving it halfway forward before obviously jamming.

But this may in part be because I had not taken the BCG apart to wipe away excess oil therein. I only cleaned the bore and wiped the lower receiver before shooting it. When I switched out my BCG with my dad's nickel-boron plated one, there was no cycling problems even using steel-cased 55gr. loads. So it's not the rifle-length gas system alone.
In any case, I always planned to use heavier bullets out of this rifle; it would on the other hand be nice to reliably cycle 55-grain FMJ's to simply break the rifle in cheaply, however---so hopefully cleaning the BCG will result in better performance. Anybody know an affordable but hotter 55 or 62gr. plinking load, though?

The best 3-shot group at 100 yards I got was an MOA from Winchester 64 grain power-core 95/5 (non-lead hollowpoint), and a 1.25 MOA using 55-grain Barnes TSX ("VOR-TX"). I'd feel comfortable hunting with either of these two rounds at this point. I got a decent 1.5-1.75 MOA group using 60-grain Nosler Partitions.
Anyone used any of these on deer out of a .223? I've heard that the Partition has a nasty tendency of splitting inside the body cavity, compromising the ability to get an exit wound. Granted, I've only heard this in the context of discussions about using the bullet in much more powerful rounds, on much bigger game (elk).

Using the Winchester, the bolt locked open on the empty mag as it's supposed to; that didn't happen with the 60gr. Nosler Partition, the 55gr. Barnes, or any other 55-grain I fired (granted, I didn't have a great sampling---didn't have time to go to the store, so I used some Silver Bear and Golden Bear 55's that my dad had, which are coated steel case with what probably figures to be a light powder load).

I have to say the recoil impulse on this rifle is incredible---I can see my hits, and the target never leaves the scope. The gas system and radial muzzle break work together great in tandem for this, especially considering how light the rifle is (a mere 6.2lbs before scope and rings).