Just set your "gottahaveititis" aside for the moment. I'm 33 years old, I have approximately 40+ firearms in my collection, and honestly, I regret approximately half the firearms I acquired over "gottahavititis" in some way or another, and know exactly what I'd rather have once I did some research or learned more...
So that means even if you did get the grey G22, I predict there's a 50% chance you'll learn more about shooting, and want a different .22 within a few years time. Say like a Ruger 10/22 because the target and competition accessories market is so huge, just as an example. So relax.
The grey "limited edition" Walther G22 will never be a high-end collectable within the next ten years. It will be worth nothing more than a used Walther G22 based on it's condition. Assuming Walther never makes another grey G22, the Blue Book will probably never put a premium higher than an extra $50 on one that's pristine New-In-Box condition in the next decade over a black or a green one. So don't sweat it.
A few people may buy into the "limited edition" BS, and might be selling theirs for a ridiculous price, but if you look around, or check gunbroker once you're living on your own, you'll find one eventually. Or, your tastes in firearms will have changed completely by then, and you won't care for the Walther one way or the other.
Here's what I would do, open a high-interest checking account, or money-market fund where you get the decent interest (for savings anyway) of 3-5%, and every time you have "the bug" for a certain gun that you can't get because of your mother, put the purchase price it would have been into that fund and save it. You'll be flush with cash when you finally do move out, and can jump-start your gun collection, ammo, a safe, all of that.
While you're saving money, to work on your mother, you need to act, and stop talking. Right now she probably has no real idea that you're serious about becoming a shooter, and just sees your desire for the Walther as another "toy". But this one is admittedly, a potentially lethal toy. And in her mind the risk isn't worth what she thinks will be 1-2 months of interest in plinking, then to be forgotten when you move onto something else.
To "work" on your mother, quit arguing with her directly. (anti-gun) Mothers are ultimately women. (
THR Women, please let me be, I'm generalizing, obviously...) And women are often motivated by
Emotion,
Guilt, and "
Mother Logic".
Despite your age, you are still her son,
Emotion is telling her that she needs to protect you from harm. She would feel endless
Guilt if she allowed you to own a firearm, and you then injured or killed yourself.
Mother Logic tells her that at least while you are under her control, if you don't own the firearm you can't be harmed.
So, back to the problem of your Mother, what do you need to attack? Simple.
Emotion,
Guilt, and
Mother Logic.
How do you do this? By turning her
Emotion and
Guilt to your advantage, and
undermining the
Mother Logic.
The Plan:
It sounds as though you've had some kind of shooting opportunities before, even though you don't own any guns of your own. Keep up with those, whatever they are.
Spend $35 and join the NRA. This shows you are serious about being a shooter.
Buy your own eye and ear protection if you don't have any already. This shows you are serious about safety.
You need to join every organized shooting sport you can legally participate in, afford to participate in, and can do so with borrowed firearms from the club, or from participants willing to help you out. This shows you are serious about shooting.
Most shotgun clubs have rental guns, and it only costs an extra dollar or two to use it. Most also have a "lesson day" where the owner or a pro will give a class on trap or skeet shooting. The good ones will charge only $20 for the lesson, and they donate the funds to youth shooting programs or the NRA etc.
Find out online, from the NRA, the local gun stores, or local ranges about all the competitions, shooter's clinics, classes etc. that you can find. Don't be shy, and explain that you're 18, have anti-gun parents, but want to participate in the shooting sports as much as you can. If you get rebuffed by some cranky shooters, keep trying. Ask how someone who doesn't have the proper rifle can participate, or if there are members willing to take you under their wing. Eventualy you'll find someone who understands we need new shooters to keep the sport and RKBA alive, and you'll find someone who gets that.
For instance, High-Power clubs/competitions make loaner M1 Garands available, because the High-Power participation is a requirement for buying a low-cost surplus M1 from the CMP. If they didn't, there'd be a chicken-n-egg problem.
So if every weekend you're out to a range or a club, and coming home with stories about how you participated in this shoot and that, how your score improved over last time, you'll get to your mother. And you'll be getting at her through the very things that are making her forbid you own guns now.
Emotionaly, parents want their children to be happy. If she sees you're truly dedicated to shooting competitions and clubs, she will begin to feel
Guilty. By participating in all the various shooting sports, clubs, and venues, it will defeat the
Mother Logic that preventing your ownership of a firearm will prevent you from being exposed to them. If you're spending a great deal of time around firearms and shooting them anyway, the
Mother Logic fails, and there is no point in preventing your owning one.
And furthermore, there's lots of people on these Internet boards, myself included, who have lots of guns in their collections, but never any time or money to shoot them. If you follow the above advice and get involved in clubs, groups, and competitions, you're better off in the long run with lots of trigger time and fewer guns, than you are with lots of guns and little trigger time. You'l be that more of a "real shooter".
One more thing.
+1000 to those who gave you the long-term advice to not marry or seriously date an anti-gun woman. You also need to be aware if a fiancée or serious girlfriend is a fence-sitter, that you make it abundantly clear that the guns stay. It's not always a crystal-clear plan in her head, but many women see their men as a "project", and will go into a relationship thinking they'll just get him to get rid of the gun collection "later". Even if she shows no desire at the time to pressure you into giving up guns, make it clear you won't, and do it repeatedly.
If she actualy loves shooting, or takes a dedicated interest after meeting you, start ring shopping.