I'd like to sight my Bushmaster M4 in for 150m, but I don't have a range that big close to me. Can someone explain to me in laymans tems how I would go about zeroing it in for 150m at lets say 50 ft. I might be able to make it out to a 100 yard range if the weather holds up. I was shooting targets the size of half dollars at 50ft a week ago, and pretty much hitting dead on, does anyone know where I would have been hitting if I was shooting at a target at 150m? I am thinking I would have been pretty high. Also, is a half dollar about the size of a human silloute (don't think I spelled that right) at 50ft?

IIRC, and I could be wrong, but for general purposes if you sight in at 50 you'll be on at 200.  Everything in between will be pretty damn close.

FWIW most of us using red-dots use the IBZ Santose method here: groups.msn.com/TheMarylandAR15ShootersSite/zeroingmethods.msnw

Sighting your rifle in at 50 yards should place you dead on 200 yards.

You'll be around 1.5" high at 100 yards and about 2-3 inches low at 300 yards.

Note: depending on what your barrel length is, (as you did not say) the figures above are for 14.5" or 16" barrels.

Mike

I sight my EOtech in at 50 yards.  Works great.