I am ready to start my AR soon and I have already decided on the lower I am going to get and where I am getting it from. I am also pretty sure where I am getting the upper from. My question is, what is the difference between Carbine and Midlength and which I should choose if they are the same price. I also need a little help on the differences in A2 and A4 and what the best direction to go on that option. I am sure it will be helpful to know that I am just wanting to build a plinker, not going to do much if any hunting or any competition.