In 100 years, your gun will be 119 years old and people will probably be hunting with laser bows and arrows and somebody will want an old shooting rifle and not be particular and will probably offer you big bucks for your rifle.
Only money won't be money anymore. They will probably have some kind of credit card that you put in a soda machine and for $80, a paper cup will come out with dehydrated soda - that you will add rain water to and have a cup of pop.
That's just my prediction. Then again, by that time, the animal rights people will have already figured out how to make guns that the animals can use to shoot back, and then we won't be safe to hunt in the woods no more anyways. So who will need guns?