I have a S&W MP15 in 5.45 and had some problems out of the box with Silver Bear 55HP. Bullets were jamming the throat hard enough to be pulled when attempting to eject a loaded round. I sent the upper back to S&W for service and it returned working OK. I honestly believe this ammo is made using .223 bullets slightly swaged to .222 diameter(still too big). RWS bullets measure
.2205 on my device. It appears most of the current ammo has proper sized bullets.
Neither the S&W or CAI AK74 like the Wolf 70 grain. It is only suitable for short range since it produces occasional keyholes @25 yards.