Originally Posted By: mj36639You do not need an action block. All you need is a good vice. I use two half inch thick pieces of polyethylene taped over the jaws(Hardwood like oak will also do). I chuck it in the vice sideways so the picatinny rail and the bottom of the upper receiver are the surfaces in contact with the polyethylene. Don't over do it. For assembling AR's you should at minimum have an armorers wrench, torque wrenches in inch and foot lbs, and moly anti seize grease in addition to common tools.
If you don't have much gunsmithing experience then an action block might be the way to go. Mistakes are expensive.
Mj, why the need for an in/lbs torque wrench? I've put together 3 ARs from scratch and have never needed this tool. I'd spend the money on a proper action block before I'd even think of an in/lbs torque wrench for an AR.
To the OP - just spring for the action block. It will make things so much easier and it is the right way to do it. You'll kick yourself for not spending the 30 bucks or so if you ruin a 100 dollar upper, especially after trying to find one to replace it. You can always rent it out too, I've always believed good tools pay for themselves.