Follow all gun safety rules, and laws….
Always wear adequate eye protection. Inferior protection such as eye or sun glasses alone can be worse than none at all.
Also respect these guns, they will break open exposed skin.
Never use metal BBs for airsoft battles, never ever.
For reference, if you hold a 340 FPS Airsoft gun 1-2 inches from a Coke can, the 6mm plastic BB will penetrate it. Don’t use thicker cans for testing at this distance. And like I say always wear adequate protection for your eyes etc….
I don’t recommend shooting airsoft guns at metal cans indoors at all. They will ricochet more readily…. Hard plastic, wood can also ricochet. Target materials that your gun is easily capable of penetrating.
Make sure you can control and contain your BBs, have adequate ballistic backstops etc. I tend to go with more than I need….
The more accurate you are, the safer you are. Practice, but practice wisely. Read what expert shooters do to train, and incorporate it into your shooting regimen….