I was contemplating teaching my grandchildren marksmanship. I want to start them out with a rifle in .22lr caliber. I was thinking of buying a Savage Rascal, but I do have a .22 upper for my AR-15 in the carbine version (adjustable stock). The length of pull collapsed is around 10 1/2 inches which is a little shorter than the Rascal. Is there any drawback to instructing these kids 8-10 years old with my AR-15? I would consider loading only one round in the magazine to start with.