I have a couple of the MC torque wrenches in in & ft lbs, been using them for years (on bikes though, not firearms) and never had an issue.
Though, actually the simple beam type torque wrenches are more accurate, never go out of adjustment and are considerably cheaper... They just suck for a lot of applications where you have to use it at any odd angle. For firearms, I'd probably just go with one of those, since you're probably not going to have access issues or have to work upside down.
...or there's always the easiest option, the Armstrong torque wrench =) Wish I had a pic of the torque wrench that goes with the Leopard (tank), it's a few feet long and just about a two man lift... went up to something like 300 lb/ft IIRC.