The breech plug on the back of the rifle is not removable in MOST traditional rifles. There are a few of them that you can take the breech out, but they tell you that in the manual that you read. Pittsburghunter gave good advise, soak the breech in a pail of water and it will not hurt to pour water or betteryet spme oil down the barrel as well. The oil (even cooking oil works)will help the bullets side back out the barrel. The idea is to kill the powder charge and get the powder too wet to ignite. Then they need to get a ball puller and pull both balls out of the barrel. They might also want to get a CO2 ball discharge unit if they do not want to pull the charge. Two balls can be a devil to get out although it can be done. I would also suggest they get a good strong range rod with female ends on both ends, and a T-handle and cleaning jag. Put the T handle in the one end and the ball puller in the other. Many times the ramrods that come with the rifles are not meant to do all that heavy power duty. After you get that ball puller screwed good and deep (as deep as you can get it) then hook the T handle in the rafters, or under your feet or some place that will not budge, and then back away nice and clean holding the rifle.

What probably happened is, they might not have cleaned the new rifle before loading. Many of them come with packing grease in them and must be cleaned. Then you have to make sure after you clean the barrel that the barrel is dry of any moisture and free of oil before loading. Also have your friend pop a couple #11 caps through the nipple before loading. This will clear the fire channel and allow the spark to get down and into the powder charge when they finally get to the point of loading and shooting.