My grandson and I were doing some shooting today with my Remington 597 quad 4 Ar-22 style rifle. Upon firing what was probably the 40th round there was a loud noise, a puff of material from the ejection port and he jerked his hand back and upon examination we found evidence that says that the previously fired round extracted but didn't eject and when the bolt came ahead it fed the next round into the chamber but the force of the empty case on the base of the new cartridge was enough to cause the primer to ignite. The cartridge was not fully chambered and had the side of it blown out right in front of the rim. The case was also swelled at the same location and was about 1/32 " shorter than a normal empty. No damage to the gun or him and after a thorough examination we fired another 100 rounds without incident. My grandson now knows why I always insist on safety glasses and hearing protection. I posted a photo in the photo section of the case. Any thoughts ?