I just saw in the Bass Pro advert. that there is a barrel exstender for a yoouth shotgun to grow with your jr. hunter. I am getting my son a Jr. 870 pump, the barrel is only 18 3/4 inches long. I may be jumping the gun but that barrel seems sooo short. The reason I go tth egun was to fit him with the stock. Has anyone used the barrel exstender and how did it work. This one just screwed in the choke threads.