I was going to buy a 20" barrel from       model 1 sales. what do I need besides the barrel and handgaurds? I also wanted to put on free floating hand gaurds. I dont want to buy a whole nuew upper. thanks

gas tube

You need a variety of punches and a barrel wrench, possibly two depending on which wrench and which free float system you decide to go with. You should probably have a torque wrench to fit the barrel wrench... and a vise mounted on a bench and an upper action clamp to hold the receiver in the vise. You may find you gas tube pretty well stuck in the front sight base... they make special tools to remove it but if you're careful you can get away with a set of vise-grips and a small hammer... Sometimes the handguards can be a pain to get off... the military manual indicates it's a two man job... they make special tools to make this an easy 30 second job. If you need to transfer the delta ring to the free float tube (like with the Comapss Lake tubes) a pair of ring pliers is a good idea. I'm probably forgetting a few things.

ok complete uper it is then thanks

Wait a minute.  You can do this, and not to sound like a "corn-ball", but you'll be glad you did it yourself.  If money's not an isuue, call Bushmaster, and ask what tools you'll need.  Home Depoy has the torque wrenches.

You'll need a small punch to take out the gas tube roll pin.  Slide the gas tube out.  then pull/push the delta ring back.  use the barrel wrench to "break" the barrel nut.  It will slide off.  The barrel's now detached.  Reverse the order to re-assemble.  Find out for sure the appropriate torque setting for the barrel nut.  Be advised.  If you set the torque of the barrel nut correctly, and the gas tube opening in the receiver does not line up w/ the cut outs in the barrel nut, go over spec. not under, ie. keep tightening slightly, until alignment.  When torquing, tighten to spec, then break again, then redo 2 more times.  That should give you the most accurate setting.  Get the technical manual for your respective rifle.  Its so easy, respectively speaking, I'd be willing to do it for you, but of course, I'm not a licensed smith, and would fear liability, but would absolutely be willing to walk you through it.  Lots o' luck S2

You can easily spend $300 for all the tools needed to do this job properly if you don't already have them. Buying a complete upper will be cheaper. But if you intend to putz around with the gun on a regular basis, having the tools is a real cost saver... I started with a 16" M4 and then got interested in match shooting... which the carbine is totally unsuited for. So over the course of 12 months, I replaced nearly every piece of the gun until I had built a 20" match grade gun, rebuilt the original M4, had almost enough spare parts to build a 3rd and was a couple of thousand dollars poorer.

Maybe an A3 upper receiver would get that 3rd one in motion... hmm...