Um...
N3rday, first, welcome to the Range!
Now...
Buy a Bushmaster upper receiver for however much that costs, and buy an assembled Mega or Stag Arms lower receiver, which only cost about $150. Compare the price of a Bushmaster lower half to a Stag Arms or Mega (which are of equal quality), and you will see why buying the gun in two separate parts can save you so much money.
And all AR-15 uppers and lowers are compatible with one another, so no worries. Also, try to buy a 'gov't' profile barrel; these maintain a smaller diameter under the handguards, while keeping it heavy beyond the Front Sight Base which helps balance the rifle a bit. Unless you have a specific reason for buying a heavy barrel, I wouldn't recommend one.
Ok... I see you aren't old enough yet and don't own one, and haven't any experience with them, yet. That's fine... and AR15.com is an excellent forum; I read there a lot.
However, there are some things that
only personal experience can teach; "Book Learnin" doesn't mean much when you're staring at a receiver, an upper, handguards, assembly pins, and wondering just what in the name of Nancy Kerrigan you've gotten yourself into.
It's true that, in
theory, all uppers and lowers ARE interchangeable.
The comfort in that thought comes to a screeching halt, however, when your new upper does NOT go onto your receiver no matter HOW big your sledgehammer is.
Assembling an AR-15 that doesn't just work, but works
well and accurately is a pretty serious undertaking, and not one I'd recommend for a beginner. There are several areas that can get you into REAL trouble, the most common likely being a bolt that's headspaced incorrectly. Or a cam pin that's a poor fit. Everything may SEEM A-OK, until you fire the thing... and there's a
very real possibility your newly built rifle is going to explode like Mt. St. Helens.
I recommend buying a ready built Bushsmaster XM15A2. It's going to funtion well and be very accurate. When you become thoroughly familiar with the rifle's functioning in
practice instead of theory, you can begin to experiment and customize.
I also recommend the heavy barrel. Yes, it does cause a a minor imbalance in the rifle... but the accuracy increase makes up for that very handily, and the weight of a cleaning kit in the buttstock can serve as a nice counterweight to help bring the rifle back into balance. The mere fact that an AR doesn't balance perfectly when held by the carrying handle does NOT mean there's anything wrong!
I'm not trying to be harsh, here... just trying to help point you in the right direction. The country NEEDS as many proficient AR shooters it can get! My point, primarily, is that you need to gain that degree of experience before you take everything you read as Gospel... some of it is completely erroneous and can literally get you killed.
We do NOT want that!!! 8)
Flyer
