Either move, or respect your Parent's wishes until you do. Find a trustworthy friend to hang onto all your stuff. I damn sure wouldn't want to keep any gun stuff outside, way too easy to steal, and thieves are like ants, when they find a crumb, they'll keep coming back until they get the whole loaf.
Put yourself in your Parent's shoes, they don't like guns, they don't want guns or gun stuff in their house, which they've likely been owning, and paying for, for a very long time. Now their son tells them he wants exactly the things they hate, and to keep the things they hate in their house, which by the way, they own, and have been paying for, for a very long time. The son, whom they love just like a son, tells them he should have the right to do all this stuff, in their home, which they own, and have been paying for, for a very long time. As much as they do love this son, they can't help but feel a bit put off, by this disturbing interest in guns. They figure, the best way to ensure safety, is to get the ammo out of the house, gun with no ammo is no worse than a baseball bat, they figure. Misguided, certainly, but it is their house, which they own, and have been paying for, for a very long time.
If you want your Parent's to treat you like a full fledged adult, you'll need to move, and show them you are capable of taking care of yourself. Trust me, when I say, it is the best thing you will EVER do for your relationship with them. They will be filled with pride, at the independant human being they raised. At this point, you will be in your own house, and can walk around naked, except for a belt, holster and glock, believe me when I say, that feels pretty damn good to do. Your Wife, on the other hand will probably roll her eyes, when she sees you like that, however.