[tHe_ZoU_cReW]

I just purchased a used Bushmaster AR-15 and I'm having trouble figuring out what kind it is. I have checked several websites and it seems I might have a mix of different kinds. I'm a first time AR-15 buyer, any help would be much appreciated.

 

[tHe_ZoU_cReW]

Thanks for all the replies! I have done a lot more research now and many of your comments helped me narrow down what I have. My main concern is the carry handle. I would like to replace the upper so I can have a rail. I hear with the right tools it is easy, I'm just a little worried to give it a go.