[MACHINE]

You don't need to worry about it wearing out. If a mag azine is stored full it wont wear out. What wears out magazines is the spring constantly being compressed and uncompressed. So storing them full is nothing to worry about. After you've put enough rounds through it it will wear out.

 

[MACHINE]

but you can buy new springs for the all the glock magazines once they do wear out.

 

[MACHINE]

I'm a little concerned about my shotguns however. You think loading three into the pipe and keeping them like that is a bad idea? The tube capacity is 8, so I figure 3 wont wear out the spring too much.

I think it should be fine. What wears out a spring is it being cycled. So if it is being constantly compressed and uncompressed it will wear out faster. So storing it like that shouldn't be a problem.