Most don't..
The washers aren't required for iron heads.
Definitely! All you need are a couple pieces of wood, some string and a few washers.
Ordinary rifles and shotguns, no. Assault rifles, yes. See link below.
To make one grill parts kit, you need 4 A washers and 5 B washers, totaling 9 washers per kit. For 100 kits, you will need 900 washers (9 washers x 100 kits). For bolts, you need 2 C bolts and 1 D bolt per kit, totaling 3 bolts per kit, which amounts to 300 bolts for 100 kits (3 bolts x 100 kits). Therefore, 900 washers minus 300 bolts results in 600 more washers consumed than bolts.
Flat steel washers, galvanised washers, ripple washers, spring washers, fibre locking washers.
MOST rifles are- but you need to refine your question to get a meaningful answer- legal for WHAT?
No, you do not.
The different types of washers available in the market include top-load washers, front-load washers, compact washers, and portable washers.
Depending on your SUV, you may only need 2 window washers. However, there are some SUV's that require two on the front, and two on the back, so really the amount of window washers you require for your specific SUV depends on the make, and model of your specific vehicle.
A home appliance store or a department store such as Sears or Lowes sells stackable washers. They can also be ordered on-line from Amazon. Garage sales are a good source of used stackable washers as people move from apartments to houses and no longer need their stackable washers.
Yes, washers can rust. I have seen many rusty washers.
You will need a gunsmith.