I would suggest looking at the Arnzen Arms reaction rod as well as the Real Avid Lug Lock Tool. Yes the Real Avid rod is aluminum, but here is my experience with it.
I have used the Real avid Lug Lock Tool daily for the last year while assembling a couple hundred AR15 uppers with both rifle and pistol length barrels. All were torqued to anywhere between 40 and 60 foot pounds. Not a single alignment pin, barrel extension, or any other part on any of the uppers were damaged in any way.
OP if you are doing occassional builds (less than 5 per year) any and EVERY ONE OF THE VARIOUS REACTION RODS, VISE BLOCK CLAMSHELLS ETC from EVERY ONE OF THE MANUFACTURERS currently on the market will serve you just as effectively as any other device out there.
In my case I have used Geissele, Arnzen Arms, MagPul BevBlock, Real Avid, and a few other tools in a production floor environment, and at home use, and have had excellent results with them ALL. Home builder? Save some money and go with Arnzen or Real Avid. If your going to build a couple of hundred uppers then go with Real Avid, Geissele, Arnzen, or Midwest Industries. ALL OF THEM WILL SERVE YOU WELL and likely outlast you.
Don't have a dog in this fight, but I do have the experience of building a few thousand uppers over the last 5 years in 2 different shop environments. jmpe.