Have a Sightron 111 5x25 on one 308, very nice, got a Bushy 4-30 elite coming for my 300 WSM, looking to get the SWFA 20 to finish refitting my main bolt guns (10FP 308). Wondering how the eye box and glass is on the 20x, they list a decent relief of 3.5" is this actual? Searched here and other places, most say get the 10x but I need more magnification to go out further (old eyes), but also need decent clarity and light transmission. Any advice appreciated.