You don't need armour plate for a pellet gun ffffs! It won't even go through 1 mm mild steel sheet.wherever you go to shoot your air rifle or air pistol, it's a great, idea if you shoot in the back garden, to have a reliable backstop. Sandbags, ect that prevent the pellet leaving your property and entering your neighbour's. I use a plate of Armour scavenged from a tank target hulk, it may seem counter intuitive, you would think in would cause pellets to glance off, but if it's hit at right angles, the pellet flattens off and simply falls at the point of impact.
The worst material is timber, as the varying hardness within the grain causes pellets to rebound in an unpredictable direction.
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