Well a pencil is soft wood and if it is a 12 ga then they must be tight but if one pencil could be made slightly smaller then they should come out. A pencil isn't that long so if you were careful and ran a small drill bit into the pencil end it might chip away at one enough to dislodge them especially if the gun has a choke which is only a couple of inches. It is easy to remove the barrel on that gun so I still would try to back them out with a dowel. Unless your son put them into the gun then pushed against the floor with a lot of weight it is hard to understand how they could be in that tightly. Have you tried to grab one of the pencils with a pair of long nose and twist?

Trying to push the mess out the muzzle, your dealing with a choke tighting or the threads for choke tube.


Remove barrel from action.
If you push toward the breach end the bore should be larger a bit and no treads. Also like some one said put some oil in the bore and allow to soak into the cotton. Then insert the dowel rod and tap with a small hammer.




Al

If you can't get it out with a dowel rod and hammer, I say take it to a gunsmith. Then, you might want to talk to your son about not messing with your guns without your permission.

I wouldn't use a hammer unless its a rubber mallet. And it needs to be pushed out from the muzzle to the chamber end for the barrel with enlarge in diameter from the muzzle down to the chamber end. If the weapon is equipped with a choke tube and it is in place, good. If not, just take it to a gunsmith as I said in my earlier post and as someone else said, DO NOT USE A DRILL OR POWER TOOLS IN THAT AREA!!!!

I was gonna say with a 12 year old.

That'll work. But I see them screaming and kicking too much for too long to successfully get the obstruction free!!!!!

Burn the pencils out with a blow torch.

I have some left over fireworks!!!! They wont fit in the barrel so maybe we can put the barrel on top of them and go from there!!!

I have some suggestions without looking at the situation. First no oil. the pencils will soak up the oil and expand making things even tighter. Second, if he put the pencils in from the muzzle, which is likely because the gun was assembled, pushing from the muzzle to the breech/chamber will only tighten the pencil's grip.
Before taking to a smith I would try using a thinner dowel maybe 1/4"-3/8" and try tapping one pencil out at a time. It is likely that if you get one out the rest will come out easily.

Many good solutions, some not so good, BUT FUNNY all the same. Reason I said to use a bit of spray lube/oil and go from muzzle to chamber is that I had a guy run a 12ga brush and patch into a 20ga and the brush became stuck. He pushed harder, no go. Tried to turn the rod, brush came off, now REALLY stuck. Would not re-align to put back on rod. Was close to the muzzle end. Brought it to me. I sprayed it with some Rem Oil, let it coat the barrel, brush and all for a minute. I then took a 1/2" wooden dowel rod, placed in my vise and from the muzzle end proceeded to tap/push the whole pile of stuff out. I then gave him a 20ga brush from my shelf and sent him on his way. I know that trying to push the stuff back out the muzzle end you will encounter the choke constriction and it will become tighter to remove. Just push it the chamber end where the bore diameter will be slightly larger and less constrictive. Just my own personal experience. That and with working on ML for years with guys who think that worm jags really work on any projectile that fit down the barrel before they came out with the CO2 blaster.