One of my coworkers is deploying to Iraq and bought an EOTECH 552.  He will be mounting it on a standard M16A2 (20 inch) barrel without any type of rail system.  He doesn't want to spend the money to buy a mount like the A.R.M.S. 39, so he bought a "brand x" carry handle mount.

Does anyone have any recommendations for zeroing an EOTECH with this mounting configuration?

Additionally, he will probably have to zero at a 25M indoor range with the M16 using M193, but he will likely be using M855 once in theater. Any thoughts on compensating for the 25m versus 50 yard (EOTECH recommended) zero and the ammunition differential.

If he uses a 75yard zero that will give him a trajectory aht is +/-2.5" from 25y to about 280y.  Lots of hold over up close if he needs to make a head shot.

When zeroing on a 25M range his group should be centered 2 1/4" to 2 3/8" below the point of aim.

Yes there will be some shifting with the switch to M855, but it won't be really noticable till a couple of hundred meters out.  Even then the rounds will hit a man-sized target with a center mass hold.

Quoted: If he uses a 75yard zero that will give him a trajectory aht is +/-2.5" from 25y to about 280y.  Lots of hold over up close if he needs to make a head shot. When zeroing on a 25M range his group should be centered 2 1/4" to 2 3/8" below the point of aim. Yes there will be some shifting with the switch to M855, but it won't be really noticable till a couple of hundred meters out.  Even then the rounds will hit a man-sized target with a center mass hold.

Thanks Forest, good information.