Went for some theraputic shootin yesterday.
I hadnt previously tried using the factory magazine that came with my Oly AR. But I figured heck, why have leave a magazine unloaded.
So, right off the bat, it doesnt have the anti-tilt follower. (I'll get pics of all this when I'm able) I loaded it and seated the magazine in my rifle, pull the charging handle back and let slam home. Safety off, sights on target, pull the trigger... "click". Nothin. Safety on, release the magazine, slowly open the action and saw there was no round chambered. Reseated the magazine and pulled the charging handle back and watched to see if it was catching the round to strip it from the magazine. Didnt even touch it. No idea why.
I unloaded the magazine which was a tremendous pain, it felt as if the rounds were in a bind from start to finish.
Loaded all the rounds into another magazine and not a single issue or snag the remainder of the time we were shootin. We fired Federal bulk pack ammo, TulAmmo steel case, Federal XM193, AETAC223, and AE AR223 (which is identical to the AETAC223 black box but saved me 2 dollars a box) We fired from the PMags and PSA USGI magazines pictured above. Not a single solitary problem otherwise...
Moral of the story, IMO the factory magazine takes up space in a range bag that would be better used for like... I dunno, several packs of chewing gum or something. Anything really, anything not the factory magazine.