I recently obtained a Bushmaster 9mm carbine and would like to put an Eotech on it.  I have an ACOG and an Aimpoint and would like to round out the collection but I've never messed with one so I have no idea which model I should get.  I will be using this carbine for plinking only and have no need for night vision compatability.  I would imagine that 50 yards will be about as far as I will shoot with this carbine so there's no need for long range sub minute of angle accuracy potential either. Just want one to get familiar with them without breaking the bank and paying for options I don't need.  

Can anyone help?

If you don't need night vision compatability, I'd go with the 512 (for the much longer battery life and cheaper and easier to find AA betteries).

an important decision for you will be how to mount the EO Tech...most prefer EO Tech mounted as far forward as possible, but still on the upper receiver pic rails...I like the QD features of LaRue mounts and some of those have a 'cantilever' feature IIRC...AAs are nice, but i chose the smaller 123 battery box which allows a 1-2" farther forward mount

I would agree with JohnthTexican. But look around the net, because I got a 551 w/ the NV for the same prices of the 512. So I got the 551 for my Bushy A2, was so impressed at 50 and 100 yds, I could not help myself, and bought a 552 for my flat top Bushmaster. I am damn glad that I got both. Since I have been to the range many times with both sights, they are outstanding, to say the least.