Ammo or Firearm?

I bought my 10 year old son a Ruger American in .243 back in September. Between the 2 of us, we've put around 50 reloads through the gun without any issues.
I took the boys hunting yesterday evening & he got a shot on a big doe, but when he squeezed the trigger, all he got was a click. Of course being a reloader, you can imagine the things that went through my mind, #1, not letting him open the bolt for several minutes & keeping the rifle pointed in a safe direction.
I inspected the round in the blind & found a very light firing pin impression on the primer, which leads me to believe something went wrong with the rifle. I've noticed a couple times that the bolt will partially open fairly easily & I've had to stop him a couple times to make sure the action was completely closed.
The good news is a 5 point stepped out about 30 minutes later & he hammered him, nice double lung. It's his 1st buck, so he went from lowest of lows to highest of highs in a span of 30 minutes.
Anyway, I'm attaching a pic of the 2 rounds in question, you can tell an obvious difference in the firing pin impressions. I guess I'd just like to know your opinions on this & specifically could the bolt being partially open have caused the problem?
Thanks for any help & info you can give.

 

Will do on the Tundra & thanks for the reply. Yes, this is the first misfire from a brand new rifle, like I said, about 50 rounds or so through it. I don't visually see any fouling & everything was cleaned & oiled last Friday before opening day & he put a 3 shot group on paper that evening when he got home from school, something I always do before a hunt; clean shoot, hunt.

 

Absolutely Highboy, Ive had my heart sink in the deer woods before, as most of us have, but that was terrible. You don't know the relief I felt when he folded that buck up like a lawn chair!.........Pheeeeww! I'll go through the bolt this afternoon with a fine tooth comb.

 

Just a drop highboy, same as hundreds of times before, then blow it out with 30 psi compressed air.
Cyclone, Yes I trim all cases on every hunting round I build. This is the 3rd .243 in my household I load for & I load .243 for 2 other rifles as well. Trust me when I say I'm very particular with my hunting rounds since a bad factory load costing me the biggest buck of my life is what started me reloading in the 1st place. I've been loading for 3 years now & have probably made up 2000 .243 without any issues. I'll double check case dimensions, but it was made in the same batch as four others that have performed without issue.

 

You got me thinkin Alpo, I left the bolt halfway open & squeezed the trigger. It sets off & the bolt falls down into the closed position, did it a couple times. Can we post videos?

 

OK guys, I'd like to link this video. It's in mp4 format, is there an easy way to convert it to an uploadable format?